UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS. 


COLLEGE  OF  AGRICULTURE. 

AGRICULTURAL  EXPERIMENT  STATION. 


THE   PEACH-WORM 


By   WARREN  T.    CLARKE. 


The  Peach-Worm  and  its  Injury. 


BULLETIN  No.    144 

(Berkeley,  September,  1902.) 


SACRAMENTO: 
a.  j.  johnston,     :      :      :      :     superintendent  state  printing. 

1902. 


BENJAMIN  IDE  WHEELER,  Ph.D.,  LL.D.,  President  of  the  University. 

EXPERIMENT  STATION  STAFF. 

E.  W.  HILGARD,  Ph.D.,  LL.D.,  Director  and  Chemist. 

E.  J.  WICKSON,  M.A.,  Horticulturist,  and  Superintendent  of  Central  Station  Grounds. 

W.  A.  SETCHELL,  Ph.D.,  Botanist. 

R.  H.  LOUGHRIDGE,  Ph.D.,  Agricultural  Geologist  and  Soil  Physicist.    (Soils  and  Alkali.) 

C.  W.  WOODWORTH,  M.S.,  Entomologist. 

*M.  E.  JAFFA,  M.S.,  Assistant  Chemist.    (Foods,  Fertilizers.) 

G.  W.  SHAW,  M.A.,  Ph.D.,  Assistant  Chemist.    (Soils,  Beet-Sugar.) 

GEORGE  E.  COLBY,  M.S.,  Assistant  Chemist.    (Fruits,  Waters,  Insecticides.) 

LEROY  ANDERSON,  M.S.A.,  Animal  Industries.  San  Luis  Obispo. 

A.  R.  WARD,  B.S.A.,  D.V.M.,  Veterinarian,  Bacteriologist. 

E.  H.  TWIGHT,  B.Sc,  Diploma  E.A.M.,  Viticulturist. 

E.  W.  MAJOR,  B.Agr.,  Dairy  Husbandry. 

A.  V.  STCJBENRAUCH,  M.S.,  Assistant  Horticulturist  and  Superintendent  of  Substations. 

*J.  BURTT  D AV T,"  Assistant  Botanist. 

H.  M.  HALL,  M.S.,  Assistant  Botanist. 

W.  T.  CLARKE,  Assistant  Entomologist. 

C.  A.  TRIEBEL,  Ph.G.,  Student  Assistant  in  Agricultural  Laboratory. 

C.  A.  COLMORE,  B.S.,  Clerk  to  the  Director. 


EMIL  KELLNER,  Foreman  of  Central  Station  Grounds. 

JOHN  TUOHY,  Patron,  ) 

y  Tulare  Substation,  Tulare. 
JULIUS  FORRER,  Foreman,  ) 

R.  C.  RUST,  Patron,  ) 

y  Foothill  Substation,  Jackson. 
JOHN  H.  BARBER,  Foreman,  ) 

S.  D.  MERK,  Patron,  ) 

y   Coast  Range  Substation,  Paso  Robles. 
J.  H.  OOLEY,  Workmanin charge,  ) 

S.  N.  ANDROUS,  Patron,  )  (  Pomona. 

y  Southern   California  Substation,   < 
J.  W.  MILLS,  Foreman,      )  (  Ontario 

V.  C.  RICHARDS,  Patron, 

T.  L.  BOHLENDER,  in  charge, 

ROY  JONES,  Patron, 

WM.  SHUTT,  Foreman, 

*  Absent  on  leave. 


y  Southern   California  Substation,   < 

y  Forestry  Station,  Chico. 
Forestry  Station,  Santa  Monica. 


The  Station  publications  (Reports  and  Bulletins)  will  be  sent  to  any. 
citizen  of  the  State  on  application,  so  long  as  available. 


CONTENTS. 


Page. 

INTRODUCTORY  NOTE  BY  C.  W.  WOODWORTH 5 

REVIEW    OF    CONDITIONS    IN    PLACER    COUNTY,    AND    PEACH-WORM 

LITERATURE 5 

WINTER  CONDITIONS  AND  WORK 8 

Hibernating  Larvje 9 

Parasitism 10 

Distribution  of  Worms  in  Orchard 10 

Pruning  as  a  Control  Measure 11 

Winter  Spraying  Experiments 12 

Resistance  to  penetration 12 

Winter  spraying 12 

Experiments  with  the  Active  Worms 13 

Artificially-induced  activity 13 

Experiments  in  penetrability 14 

SPRING  CONDITIONS  AND  WORK 15 

Spraying  Experiments 15 

Danger  to  blossoms  ._ 15 

Spring  History  of  the  Worm  .. 18 

Escape  from  burrow 18 

Attack  on  buds 19 

Results  on  Bud-Worm  of  Earlier  Work  .  20 

The  pupa 22 

Pupation 22 

Campaign  Against  Pup^:..- 23 

Band  traps 23 

Oil  spraying 24 

The  Moth 25 

Lantern  traps 25 

Egg-Laying 26 

Worms  of  Second  Generation 26 

Attempt  to  poison  these  worms 27 

STUDY  OF  THE  FRUIT  WORM 29 

The  First  Fruit  Worms -. 29 

Pupation 30 

The  Moth  and  Egg-Laying 3L 

Worms  of  Third  Generation 31 

FALL  HISTORY  OF  THE  INSECT 31 

Peach-Worm  Calendar 32 

RESULTS  OF  SPRAYING  EXPERIMENTS 32 

Tables  Showing  Results  on  Different  Varieties  . 33 

Unsprayed  Trees 36 

Sprayed  Trees 36 

Failure  of  IXL  compound 36 

The  use  of  oil  for  killing  the  pupae 36 

Winter  spraying  with  lime,  salt  and  sulfur 37 

Spring  spraying  with  lime,  salt  and  sulfur _ 37 

Miscellaneous  Results 38 

Loss  due  to  adjacent  infested  orchards 38 

Loss  from  careless  work 39 

.  Saving  by  careful  work 40 

Use  of  oil  and  distillate  emulsion 40 

GENERAL  CONCLUSIONS  AND  RECOMMENDATIONS 42 


THE  PEACH-WORM. 


By  WARREN  T.  CLARKE. 


Introductory  Note. — The  investigations  reported  in  this  bulletin  were  undertaken 
at  the  request  and  with  the  cooperation  of  the  peach-growers  of  Placer  County.  At  the 
Farmers'  Institutes  held  last  winter  at  Loomis  and  Newcastle  this  Department  was 
urged  to  help  in  the  fight  against  the  peach- worm. 

The  work  was  finally  made  possible  through  the  agreement,  by  certain  public-spirited 
gentlemen  at  Newcastle,  to  provide  for  the  local  expenses  of  the  study.  These  expenses 
were  finally  assumed  by  the  Supervisors  to  the  sum  of  $330.  The  University  contributed 
the  services  of  the  Assistant  Entomologist,  W.  T.  Clarke,  who  began  his  work  on  the 
2d  of  January  of  the  present  year,  having  his  headquarters  at  Newcastle. 

Early  in  February  a  press  bulletin  was  issued,  as  a  result  of  this  study,  recommend- 
ing a  method  of  treatment  which  has  proven  to  be  remarkably  efficient.  The  majority 
of  growers  in  Placer  County,  and  doubtless  many  elsewhere,  availed  themselves  of  this 
information  and  have  already  reaped  very  material  benefits. 

The  people  of  Placer  County  have  left  nothing  undone  that  would  aid  Mr.  Clarke  in 
this  study,  and  this  bulletin  represents  the  results  of  this  year's  spraying  experience  of 
practically  the  whole  acreage  of  the  largest  fresh-fruit-shipping  section  of  the  State. 

Many  points  in  the  life  history  of  the  peach-worm  have  been  cleared  up  in  this  study, 
and  the  facts  have  been  found  to  be  in  many  important  particulars  at  variance  with  the 
accounts  of  the  insect  heretofore  published. 

C.  W.  Woodworth. 


Probably  the  most  serious  peach  pest  in  California  is  the  peach-worm 
(Anarsia  lineatella  Zell.),  a  widely  distributed  insect,  attacking  also 
plums  and  apricots,  but  so  far  as  now  known,  confining  its  attack  to  the 
stone  fruits.  Its  greatest  and  most  evident  damage  is  the  injury  to  the 
fruit  of  the  peach,  grown  for  Eastern  shipment  as  fresh  fruit.  In  some 
seasons  this  loss  has  aggregated  as  high  as  thirty  per  cent  of  the  entire 
crop.  Some  idea  of  the  magnitude  of  the  damage  may  be  gained  from 
the  following  table,  which  presents  the  losses  suffered  by  the  growers  of 
fresh  fruit  alone  during  the  past  four  years: 

Table  Showing  Loss  Due  to  the  Work  of  the  Peach-Worm  in  Fresh  Fruit. 

Not  Injured.  Injured  by  Worm. 

Shipped.  Not  Shipped. 

, * (  t *• , 

Year.                                                            Carloads.                  Value.  Per  cent  Lost.  Value  Lost. 

1898 1,103  $661,800                    25  $220,000 

1899 2,625  1,575,000                    20  393,000 

1900 1,361                     816,600                    25  272,000 

1901 1,901  1,140,600                    30  488,000 

Total  in  four  years 6,990  $1,194,000  25  $1,373,000 

These  figures  are,  of  course,  only  estimates,  but  are  believed  to  be 
safely  on  the  conservative  side  and  understate  the  actual  loss  in  fruit 
suffered  in  the  seasons  under  consideration. 


b  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

To  the  aggregate  loss  shown  in  this  table  of  over  one  and  one  third 
million  dollars,  must  be  added  the  loss  in  value  of  the  fruit  grown  for 
canning  and  drying. 

The  damage  done  by  the  insect  is  by  no  means  confined  to  the  fruit, 
but  great  injury  is  at  times  also  done  to  the  trees  themselves.  The 
insect  feeds  in  the  spring  upon  the  new  growth  as  soon  as  it  appears, 
long  before  the  peaches  are  formed,  causing  this  new  growth  to  die  just 
as  it  is  starting.  It  is  known  at  this  time  as  the  "  bud-worm,"  and  its 
attack  has  frequently  been  so  severe  as  actually  to  cause  the  death  of 
the  infested  trees.  In  parts  of  California  the  loss  in  this  way  has  been 
in  some  regions  very  heavy,  but  the  actual  money  loss  in  cases  of  this 
kind  can  hardly  be  accurately  estimated. 

In  spite  of  these  great  losses  the  peach  is  considered  a  very  profitable 
crop  in  many  parts  of  California,  being  grown  to  a  considerable  extent 
in  the  Vaca  Valley  and  adjacent  valleys  of  the  foothills  of  the  Coast 
Range  of  mountains,  in  the  Santa  Clara  Valley,  and  in  some  of  the  more 
favorable  portions  of  the  Sacramento  and  San  Joaquin  valleys,  as  well 
as  in  the  Placer  County  region,  where  these  investigations  were  mostly 
made. 

The  Placer  County  peach  section,  which  is  probably  the  best,  and 
certainly  largest,  green-fruit-producing  section  in  the  State,  is  in  the 
Sierra  foothill  region,  at  an  elevation  of  from  600  to  1,200  feet  above 
sea-level.  The  large  proportion  of  the  peach  orchards  of  this  section 
are  to  be  found  in  the  scope  of  country  extending  from  Auburn  on  the 
northeast  to  Rocklin  on  the  southwest,  a  distance  of  fourteen  miles 
along  the  Central  Pacific  Railway,  and  covering  the  country  for  from 
three  to  ten  miles  on  either  side  of  this  railway.  Loomis,  Penryn,  and 
particularly  Newcastle  are  shipping  points  in  this  region. 

From  the  region  above  described  fully  ninety  per  cent  of  the  fresh- 
peach  shipments  of  the  State  are  made,  and  the  actual  loss  from  the 
peach-worm  here  is  most  clearly  felt. 

The  peach-moth  has  been  long  known  to  entomologists,  having  been 
originally  described  as  a  European  insect  in  1839  by  C.  P.  Zeller,  in  Isis, 
p.  190.  In  1860,  Dr.  B.  Clemens  redescribed  the  moth  in  Proc.  Acad. 
Nat.  Sci.,  Phil.,  p.  169,  as  Anarsia  pruinella,  and  in  1872  the  same 
writer  identified  this  insect  as  the  A.  lineatella  of  Zeller  in  "Tineina  of 
North  America,"  p.  36. 

Again  in  187-2,  W.  Saunders,  in  Annual  Report  Entom.  Soc.  Ontario, 
p.  15,  describes  a  worm  attacking  the  root  and  crown  of  the  strawberry, 
and  considers  it  to  be  identical  with  the  peach-worm.  This  belief  is 
shared  by  other  writers,  until  the  work  of  A.  B.  Cordley,  reported  in 
Bulletin  45,  Oregon  Agric.  Exper.  Station,  June,  1897,  p.  123,  made  it 
very  probable  that  the  peach-worm  and  the  strawberry  crown-borer  are 
distinct  insects. 

In  July,  1872,  T.  Glover,  in  Entom.  Rec.  Monthly  Rep.,  U.  S.  Dept. 
Agric,  pp.  304-305,  reports  the  peach-worm  in  Maryland  and  Virginia. 


peach-worm:  experimental  orchards.  7 

In  1879,  J.  H.  Comstock,  in  Rept.  U.  S.  Dept.  Agric,  p.  255,  briefly 
notes  its  twig-boring  habit  and  describes  the  pupation  of  the  second 
generation  on  the  peach. 

The  next  work  of  economic  importance  was  that  of  Edw.  M. 
Ehrhorn,  reported  by  Alexander  Craw  in  Bulletin  67,  California  State 
Board  of  Horticulture,  1893  (1894),  page  9;  it  showed  that  the  insect 
wintered  in  the  early  larval  form  in  chambers  hollowed  out  in  the  bark 
of  the  crotches  of  the  branches  of  the  trees.  Mr.  Ehrhorn's  investiga- 
tions were  continued  in  1896-97  by  C.  L.  Marlatt  at  Washington  with 
material  furnished  by  Mr.  Ehrhorn  from  California,  and  the  results 
were  published  in  1898  in  Bulletin  10  (new  series),  U.  S.  Dept.  of  Agric, 
Div.  of  Entom.,  pp.  7-20. 

The  insect  has  been  reported  by  other  writers  as  being  present  in 
Delaware,  Illinois,  Colorado,  and  Washington;  and  doubtless  occurs 
in  all  peach-growing  localities. 

The  article  by  Marlatt  gives  the  fullest  account  of  the  insect  that  has 
yet  appeared.  This  work  was  unfortunately  done  under  rather  unnat- 
ural conditions,  and  does  not  agree  in  many  instances  with  the  actual 
orchard  habits  of  the  insect  here  in  California.  The  other  Eastern 
observations  were  very  fragmentary,  and  required  verification  here 
before  being  of  much  value  as  a  basis  for  a  scheme  of  repression. 

The  writer  was  somewhat  acquainted  with  the  insect  from  previous 
studies  in  the  Santa  Clara  Valley,  and  from  the  2d  of  January  has  kept 
it  under  continuous  observation  in  breeding-cages,  on  a  large  covered 
tree,  and  in  the  orchards  in  Placer  County,  particularly  about  New- 
castle, which  was  headquarters  for  the  investigation.  No  pains  were 
spared  to  make  the  work  as  exhaustive  as  possible. 

The  location  of  the  larger  part  of  the  experiments  was  in  an  orchard 
one  eighth  of  a  mile  southeast  of  Newcastle,  which  will  be  referred  to  as 
the  Newcastle  station.  Another  station  was  located  in  an  orchard  two 
miles  north  of  Newcastle,  which  we  designate  as  the  Ophir  station;  a 
third,  in  an  orchard  one  mile  east  of  Newcastle,  known  as  station  A; 
a  fourth,  in  an  orchard  one  and  a  half  miles  south  of  Newcastle,  called 
station  B;  and  a  fifth,  in  an  orchard  three  miles  northeast  of  Loomis, 
and  referred  to  as  station  C.  These  five  places  include  some  two  hun- 
dred acres  of  peach  trees  of  many  varieties.  The  number  of  trees 
treated  in  the  experiments  carried  on  in  these  places  amount  to  a  total 
of  some  12,000. 

The  experiments  were  not  confined  to  these  places,  however,  for 
work  was  done  in  many  other  orchards.  The  work  done  in  these  other 
orchards  was  sufficient  to  secure  some  valuable  results,  and  some  four- 
teen of  these  in  which  records  were  kept  are  reported  in  the  following 
pages  in  conjunction  with  the  work  and  results  on  the  different  stations. 
These  other  places  will  be  referred  to  by  numbers. 


5  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT    STATION. 

WINTER  CONDITIONS,  AND  WORK  OF  THE  WORM. 

The  investigation  of  the  peach-worm  began  by  a  study  of  the  insect 
in  its  winter  burrow  within  the  bark,  at  the  crotches  of  the  tree.  The 
position  on  the  tree  generally  chosen  for  the  purpose  is  the  crotch  formed 
where  the  new  wood  joins  that  of  the  previous  year,  though  older 
crotches  are  occasionally  selected.  There  appears  to  be  something  in 
the  physical  make-up  of  the  crotch  bark  that  is  preferred  by  the  worm 
for  its  winter  quarters.  When  the  same  sort  of  new  bark  is  formed 
in  other  situations,  such  as  that  growing  over  a  wound  in  the  older 
part  of  the  tree,  then  the  worm  may  also  be  commonly  found  in  this 
situation.  The  position  taken  in  the  crotches  is  that  which  brings  the 
hibernating  chamber  invariably  on  the  upper  exposure  of  the  limbs. 
We  have  never  found  the  burrows  on  the  lower  side. 


Fig.  1.    Twig  showing  winter 
burrow,  natural  size. 


Fig.  2.    The  same  burrow  shown  in 
Fig.  1,  enlarged. 


The  location  of  these  burrows  may  be  discovered  by  the  presence  of  a 
small  mound,  which  is  in  reality  a  silken  tube  covered  with  a  complete, 
closely-arranged  covering  of  minute  pellets  of  masticated  bark.  The 
color  of  these  pellets  on  a  recently  constructed  tube  is  a  reddish-brown, 
of  the  same  shade  shown  by  the  bark  some  hours  after  it  has  been  cut, 
and  changes  to  a  darker  brown  after  continued  exposure  to  the  weather. 
These  mounds  are  completed  in  the  fall  preliminary  to  the  worm's  going 
into  winter  quarters.  They  are  not  added  to,  nor  increased  in  length, 
during  the  winter,  even  where  we  have  carefully  clipped  away  the  tube. 
Several  such  uncovered  burrows  were  kept  under  observation  from 
January  3d  to  March  5th  without  any  additions  being  made.  The 
worms  on  this  latter  date  were  removed  and  found  to  be  alive  and 
apparently  healthy.  The  pellet-covered  tubes,  shown  in  natural  size  in 
Fig.  1,  are  rather  minute   and  will   usually  escape  notice.     They  are 


peach-worm:  winter  conditions.  y 

quite  characteristic  in  form  and  are  easily  recognized  in  any  of  their 
modifications  by  the  aid  of  a  glass,  when  the  bead-like  arrangement  of 
the  pellets  on  the  tubes,  as  shown  in  Figs.  2  and  3,  will  be  noted.  The 
hibernation  burrows  are  cut  out  well  beneath  the  bark,  and  extend  into 
the  cambium  layer.  In  the  majority  of  cases  they  are  found  just 
beneath  a  thin  layer  of  the  greener  cells  below  the  brown  bark,  while 
the  greater  part  of  the  burrow  is  in  the  yellowish  portion  of  the  cambium. 
The  burrow  is  generally  about  three  times  as  large  as  the  worm  occupy- 
ing it,  and  is  lined  with  silk.  The  silken  tube  previously  referred  to, 
which  projects  from  the  mouth  of  the  burrow,  is  an  extension  of  this 
lining.  This  silk-lined  chamber  is  very  efficient  as  a  protection  from 
all  inclemencies  of  the  weather,  and  likewise  protects  the  worm  from 
sprays  in  a  remarkable  manner,  as  will  be  seen  from  the  experiments 
detailed  later  on. 


mfM 


Fig. 


3.    The  same  burrow  laid  open,  showing  how  the  worm  begins 
its  spring  work. 


Hibernating  Larvx. — The  hibernating  larvae  occupying  the  silk-lined 
burrows  are  commonly  found  at  the  deep  end  of  the  chambers  with  their 
heads  toward  the  silken  tubes,  though  they  may  be  found  in  almost  any 
position.  Their  age,  as  they  were  found  in  January,  is  not  known, 
though  there  was  some  variation  in  size  and  two  stages  of  growth  were 
present,  judging  by  the  sizes  of  the  heads.  These  hibernating  worms 
ranged  from  1  to  \\  millimeters*  in  length.  The  abdomen  and  thorax 
varied  in  color  in  different  specimens  from  light  brown  to  white,  the 
head  and  cervical  and  anal  plates  being  a  shining  black,  in  sharp  con- 
trast to  the  rest  of  the  body.  The  space  between  the  second  and  third 
thoracic  segments  is  noticeably  and  characteristically  lighter  in  color 
and  more  evident  than  that  between  any  of  the  other  segments.  The 
creature  is  ornamented  with  hairs,  which  spring  singly  from  minute 

*A  millimeter  is  equal  to  -^  of  an  inch. 


10  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

tubercles  and  which  are  rather  sparsely  scattered  over  it.  The  general 
appearance  of  the  larva  and  the  position  of  the  thoracic  and  abdominal 
legs  are  shown,  very  much  enlarged,  in  Fig.  4.  No  perceptible  change 
in  the  size  or  color  of  the  insect  occurred  from  January  2d  until  about 
March  1st. 

Parasitism. — The  insect  was  to  a  slight  extent  attacked  by  parasites 
during  the  hibernation  period,  but  the  amount  of  benefit  derived  from 
this  source  was  extremely  small  in  the  Placer  County  region  during  the 
season  of  1902.  The  larvae  of  a  Proctotrupid  fly  was  found  destroying 
the  worms  in  three  different  cases,  while  a  predaceous  mite,  which  was 
probably  the  same  as  that  mentioned  by  C.  L.  Marlatt  (Bui.  10,  n.  s., 
U.  S.  Dept.  of  Agric,  Div.  of  Entom.,  p.  17)  was  occasionally  noted. 
The  total  number  of  hibernating  worms  destroyed  by   these  natural 


Wintering  larva;  much  magnified. 


enemies  was  less  than  one  per  cent.  We  were  unable,  during  the  season 
of  1902,  to  confirm  the  statement  made  by  Mr.  Marlatt  in  the  above- 
cited  publication,  that  this  mite  "causes  the  death  of  from  75  to  95  per 
cent  of  the  young  larvre." 

DISTRIBUTION    OF    WORMS    IN    ORCHARDS. 

The  distribution  of  the  hibernating  worms  was  very  general  and  uni- 
form over  infested  orchards,  and,  except  where  modified  by  evident 
local  conditions,  the  worms  were  about  equally  numerous  on  all  the 
trees.  Indeed,  as  far  as  hibernation  is  concerned  the  variety  of  the 
peach  seemed  of  no  significance,  the  worms  being  found  at  this  season 
evenly  distributed  among  the  early,  midsummer,  and  late  trees. 

There  are  some  modifying  conditions,  however,  that  do  result  in 
certain  trees  being  more  heavily  infested  than  their  neighbors.  It  is  a 
custom  in  many  orchards  to  throw  out  the  wormy  fruit  in  piles  near 
the  packing-sheds.  These  sheds  are  generally  placed  among  the  trees, 
and  the  piles  of  rejected  wormy  fruit  are  thus  usually  in  close  proximity 
to  these  trees.  It  was  found  that  where  this  custom  prevailed  these 
neighboring  trees  were  much  more  heavily  infested  than  were  the  rest 


peach-worm:  winter  control  measures. 


11 


*mk3o 


30 


20 


of  the  trees  in  the  orchard.  This  condition  is  illustrated  by  the  accom- 
panying diagram  (Fig.  5),  which  is  of  a  packing-shed  and  orchard  in 
the  district  under  investigation.  The  trees  in  this  orchard  are  five  years 
old,  strong  and  healthy,  but 
the  fruit  the  previous  season 
was  very  wormy.  The  trees 
generally  in  this  orchard  had 
from  five  to  eight  hibernat- 
ing larvae  in  them  when 
investigated. 

The  distribution  here  had 
been  very  plainly  affected 
by  the  local  conditions.  A 
similar  state  of  affairs  was 
found  to  be  present  wherever 
similar  conditions  exist. 

In  certain  orchards  it  has 
been  the  habit  to  distribute 
the  wormy,  unmarketable 
fruit  about  the  less  vigorous 
trees  as  a  fertilizer.  It  was 
found  that  these  trees  were 
infested  from  five  to  ten 
times  as  heavily  as  the  rest 
of  the  orchard. 

The  practice  of  allowing 
the  wormy  fruit  to  remain  in 
such  a  condition  that  the 
woms  may  fully  develop  and  carry  on  the  infection  could  be  easily 
avoided  by  covering  the  piles  with  earth,  when  the  heat  developed  by 
fermentation  would  be  sufficient  to  destroy  the  worms. 


75- 


'kc h- c u.  116. •'-':■}'-  • 


6C 


Packing,  5hed 


Fig.  5.    Diagram  of  a  portion  of  an  orchard  showing 
abundance  of  worms  on  trees  near  cull  pile. 


PRUNING    AS    A   CONTROL    MEASURE. 

Some  have  supposed  that  in  the  process  of  pruning,  many  of  the 
worms  in  their  winter  quarters  were  destroyed.  The  percentage  of  the 
worms  so  destroyed,  however,  is  usually  very  small,  as  we  have  deter- 
mined in  many  cases  by  actual  count.  This  counting  of  the  hibernating 
chambers  in  trees  before  and  after  the  pruning  showed,  on  an  average, 
that  generally  one  worm  in  ten  was  cut  away.  As  the  prunings  are 
removed  from  the  orchard  and  destroyed  the  hibernating  worms  in 
them  are  effectually  disposed  of,  but  the  destruction  of  only  ten  per  cent 
is  not  a  very  good  degree  of  efficiency. 


12  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

No  great  dependence  can  therefore  be  placed  in  the  ordinary  pruning 
as  a  control  for  the  peach-worm. 

WINTER  SPRAYING    EXPERIMENTS. 

The  practice  usually  advised  for  fighting  the  peach-worm  is  to  spray 
the  trees  in  the  same  way  as  for  scale  insects.  The  field  work,  therefore, 
began  by  an  attempt  to  find  the  best  spraying  material  for  this  purpose. 
A  series  of  experiments  was  undertaken,  with  the  idea  of  determining 
the  practicability  of  killing  the  insect  at  this  time.  These  experiments 
began  January  9th,  and  were  continued  until  past  the  middle  of  the 
month.  Kerosene  emulsion  was  the  first  material  tried.  The  emulsions 
were  made  up  according  to  the  following  formulae: 

1st.     150°  kerosene,  1-J  pints;  sour  milk,  1  pint;  water,  2  gallons. 

2d.  \  pound  hard  soap  dissolved  in  2  quarts  of  water  and  1  pint  of 
kerosene. 

Each  of  these  emulsions  was  diluted  with  two  gallons  of  water,  and 
infested  trees  were  thoroughly  sprayed  with  these  mixtures;  but  to  our 
surprise,  when  the  worms  were  examined,  to  ascertain  the  results  of  the 
treatments,  no  effect  whatever  was  observable. 

Resistance  to  Penetration. — Upon  the  failure  of  the  above  experiments 
we  began  a  study  in  the  laboratory.  In  order  to  test  the  penetration  of 
these  substances  under  the  most  severe  conditions,  we  submerged  in 
the  emulsion  twigs  containing  the  worms  and  kept  them  there  two 
days.  When  the  twigs  were  taken  out  after  this  soaking  for  forty-eight 
hours,  the  worms  were  found  none  the  worse  for  the  experience.  That 
there  might  be  no  doubt  as  to  the  killing  power  of  the  emulsions  used, 
the  material  was  sprayed  on  several  worms  with  an  atomizer,  and  these 
worms  were  dead  dn  from  forty-five  minutes  to  one  hour  and  fifteen 
minutes.  The  lime,  salt  and  sulfur  spray  was  experimented  with,  with 
exactly  the  same  results;  showing  the  same  lack  of  power  to  penetrate 
to  the  worm  in  its  winter  home,  but  killing  readily  when  it  was  applied 
to  its  unprotected  body.  The  same  results  were  also  obtained  with  the 
distillate  oil  (28°)  and  a  number  of  other  sprays  used.  This  whole 
series  of  experiments  indicated  the  futility  of  attacking  the  worm  while 
the  winter  conditions  prevailed,  at  least  under  the  conditions  found  in 
Placer  County. 

Winter  Spraying. — Notwithstanding  the  fact  that  our  experiments 
had  indicated  the  comparative,  futility  of  winter  spraying  as  a  control 
for  the  peach-worm,  we  made  careful  observations  on  the  few  orchards 
that  were  sprayed  at  this  time  with  the  lime,  salt  and  sulfur.  The 
conditions  found  on  these  places  were  similar  in  character.  They  were 
all  strongly  infested  with  the  hibernating  larvae.  The  spray  material 
was,  in  each  case,  carefully  prepared  and  applied  to  the  trees;  the  effort 


peach-worm:  winter  control  measures.  13 

being  made  to  cover  them  completely,  so  that  the  treatments  should  be 
as  effective  as  possible.  The  poor  results  of  these  sprayings  will  be  seen 
in  the  tables  on  pages  33  to  35,  orchards  Nos.  A,  C,  1,  7,  8,  9,  and  10- 
Smaller  experiments  at  the  Newcastle  station,  made  so  as  to  keep  the 
trees  under  closer  observation,  gave  exactly  similar  results. 

Besides  this  work  with  the  lime,  salt  and  sulfur,  we  sprayed,  early 
in  February,  six  trees  (three  Hales  and  three  Salways)  at  the  Newcastle 
station  with  kerosene  oil  emulsified  with  soap  in  the  proportion  of  1 
part  of  the  emulsion  to  8  parts  of  water  on  one  tree  of  each  of  these  two 
varieties;  the  same  emulsion  in  the  proportion  of  1  to  10  on  two  of  the 
other  trees,  and  a  mechanical  mixture  of  kerosene  oil  1  part  to  water  3 
parts  on  two  more  trees. 

And  also  at  the  Ophir  station  we  sprayed,  in  the  middle  of  February, 
forty-eight  Salway  peach  trees  with  the  so-called  Hercules  emulsion  of 
28°  distillate  oil,  using  the  proportions  1  part  of  emulsion  to  8  parts 
and  to  12  parts  of  water. 

In  all  of  these  experiments  no  differences  between  the  sprayed  and 
the  checked  trees  could  be  distinguished.  The  account  of  the  ultimate 
condition  is  given  on  page  35. 

experiments  with  the  active  worm. 

Artificially-Induced  Activity. — The  fact  having  become  thus  evident 
that  any  work  done  toward  killing  the  hibernating  worm  must  be 
delayed,  at  least  until  the  beginning  of  the  period  of  its  activity,  we 
endeavored  to  ascertain  when  this  activity  could  be  expected  to  occur. 
Branches  containing  hibernating  larvae  were  placed  with  their  cut  ends 
in  moist  sand  in  a  room  in  which  the  day  temperature  was  kept  at  70° 
Fahr.  and  the  night  temperature  fell  to  about  40°  Fahr.  They  were 
examined  from  time  to  time,  and  by  the  end  of  the  fourth  day  an  appre- 
ciable activity  was  noted  on  the  part  of  the  worms.  Upon  opening  their 
burrows  at  this  time  they  were  found  to  be  quite  lively  in  their  motions. 
At  the  end  of  the  sixth  day  the  worms  had  begun  to  tear  away  the  cov- 
ering portion  of  the  silk  lining  to  their  winter  homes.  On  the  four- 
teenth day  worms  began  to  come  to  the  surface,  and  continued  to  do  so 
for  three  days,  when  they  had  apparently  all  come  out. 

To  arrive  at  the  effect  of  continued  warm  conditions,  a  number  of 
the  chips  containing  winter  larvae  were  cut  from  the  trees.  The  chips 
were  kept  steadily  at  about  the  body  temperature  of  the  experimenter. 
The  effect  of  this  treatment  was  rapid,  as  in  one  case  worms  had 
worked  their  way  out  of  their  burrows  at  the  end  of  the  fourth  day,  and 
the  longest  time  taken  to  emerge  was  six  days. 

Considering  that  it  was  possible  that  the  worms  might  be  brought 
forth  from  the  winter  quarters  by  exceptional  warm  temperature  condi- 
tions occasionally  occurring  during  the  winter,  some  of  the  worms  were 


14 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


kept  under  observation  after  they  had  come  to  the  surface,  to  deter- 
mine if  they  would,  in  the  absence  of  green  food,  re-imbed  themselves. 
A  number  of  these  worms,  and  also  a  number  that  had  been  cut  from 
their  burrows,  were  placed  upon  fresh  uninfested  twigs,  and  their  actions 
noted.  During  the  first  twenty-four  hours  the  worms  were  all  more  or 
less  active  and  restless,  moving  about  a  great  deal,  but  with  no  apparent 
definite  object.  They  became  less  active  during  the  second  twenty-four 
hours,  but  made  no  effort  that  could  be  recognized  as  an  attempt  to  make 
new  burrows.  A  progressively  diminished  activity  continued  during 
the  third  twenty-four  hours  and  during  the  remainder  of  the  time  of  the 
experiment,  the  worms  finally  dying  without  re-entering  the  bark. 
This  experiment  was  carried  on  in  duplicate,  one  set  being  under  natural 
temperature  conditions,  and  the  Other  in  a  room  where  the  temperature 
varied  between  day  and  night  from  about  70°  Fahr.  to  about  40°  Fahr. 
The  results  were  the  same  in  both  sets.  These  experiments  would  seem 
to  indicate  that  if  continued  warm  weather  prevailed  during  the  winter, 
numbers  of  the  worms  might  come  to  the  surface,  and  in  the  lack  of  the 
necessary  food  would  perish. 

Experiments  in  Penetrability. — A  series  of  experiments  as  to  the 
penetrability  of  the  winter  quarters  of  the  worms,  after  the  worms  had 
become  active  under  the  influence  of  an  elevated  temperature,  was 
now  undertaken.  The  sprays  were  the  same  as  those  previously 
described,  and  the  work  and  the  results  are  shown  in  the  following 
tables: 


Table  Showing  Effects  of  Sprays  on  Winter  Quarters  of  the  Worm. 
After  6  Days  of  High  Temperature. 

Spray  Used. 


Kerosene  and  milk  emulsion. 
Kerosene  and  soap  emulsion 

Distillate  emulsion 

Lime,  salt  and  sulfur 


Effects  at  End  of— 

1  hour. 

2  hours. 

3  hours. 

4  hours. 

Alive 

Alive,  feeble 

Feeble 

Dead 

Alive 

Alive,  feeble 

Dead 

Alive 

Alive,  feeble 

Dead 

Alive 

Alive,  feeble 

Dead 

After  8  Bays  of  High  Temperature. 

Kerosene  and  milk  emulsion ...  Alive  Alive,  feeble  Dead 

Kerosene  and  soap  emulsion Alive  Alive,  feeble  Dead 

Distillate  emulsion. ._  .. Alive,  feeble  Dead  

Lime,  salt  and  sulfur Alive,  feeble  Dead  


The  results  obtained  in  these  experiments  seemed  definite  enough  to 
prove  that  spraying  operations  against  the  peach-worm,  to  be  successful, 
should  be  delayed  until  such  time  as  the  worm  became  active.  Growers 
were  therefore  advised  to  delay  their  spraying  operations  until  the  worm 
had  eaten  out  of  its  winter  nest  upon  the  coming  of  the  warm-weather 
conditions  of  spring. 


peach-worm:  spring  conditions.  15 

SPRING  CONDITIONS  AND  WORK. 

The  next  stage  in  the  investigation  was  the  planning  and  carrying-out 
of  extensive  field  tests,  based  on  the  observations  and  experiments  just 
described. 

SPRAYING    EXPERIMENTS. 

The  experiments  undertaken  at  this  time  were  of  two  classes — those 
with  lime,  salt  and  sulfur  mixture,  and  those  with  oils  and  emulsion. 
Of  the  former  there  was  a  large  series  under  the  direct  supervision  and 
control  of  the  writer,  and  a  much  larger  amount  of  spraying  was  done  by 
farmers  in  accordance  with  our  advice.  Fully  eighty  per  cent  of  the 
spraying  done  in  Placer  County  this  year  was  timed  according  to  these 
directions. 

In  the  orchards  of  the  five  stations  established  for  this  study  some 
12,000  bearing  peach  trees  were  sprayed  with  the  lime,  salt  and  sulfur 
compound.  As  full  records  as  possible  were  kept  of  the  spraying  in  the 
whole  region  where  the  investigation  was  made,  which  amounted  to  over 
two  million  trees  which  received  this  same  treatment. 

Spraying  was  done  at  this  time  on  five  different  places  with  the  I  X  L 
compound,  a  proprietary  preparation  quite  widely  advertised.  These 
places,  which  will  be  referred  to  as  Nos.  2,  3,  4,  5,  and  6,  were  treated 
with  the  compound  named,  following  the  exact  directions  given  for  the 
work  by  the  manufacturers.  The  material  was  first  applied  just  as  the 
buds  were  bursting,  and  this  was  followed  by  another  application  about 
one  month  later.  Altogether  some  8,300  peach  trees  were  sprayed  on 
these  five  places  with  this  compound.  A  close  watch  was  kept  on  these 
orchards,  for  it  was  felt  that  if  the  material,  which  contains  lime,  salt 
and  sulfur,  would  control  the  worm,  the  fact  that  it  can  be  purchased 
ready-made  and  comparatively  cheap  would  be  much  in  its  favor.  The 
results,  however,  were  very  unsatisfactory,  as  will  be  seen  below. 

We  experimented  also  with  distillate  oils,  both  in  mechanical  mixture 
with  water  and  in  emulsions.  A  number  of  these  oils  and  emulsions 
were  furnished  us  by  the  Densmore-Stabler  Refining  Company  of  Los 
Angeles  for  the  purpose  of  experimentation.  These  were  the  28°  dis- 
tillate treated  and  untreated,  and  the  33°-35°  distillate  and  emulsions 
made  up  from  these  oils. 

Danger  to  Blossoms. — All  this  spraying  in  the  orchards  was  timed  as 
far  as  possible  by  the  condition  of  the  trees;  that  is,  it  was  done  gener- 
ally just  before  they  burst  into  blossom.  In  very  many  instances  the 
spraying  could  not  be  done  until  the  trees  were  in  full  bloom.  It  has 
not  usually  been  thought  possible  to  spray  when  the  blossoms  were  out 
without  seriously  injuring  or  killing  them,  especially  with  a  spray  of 
this  strength. 


16  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

Spring  spraying  must  be  done  nearly  at  blossoming  time,  and  may 
easily  be  delayed  by  various  causes  until  the  trees  are  in  blossom; 
much  attention  was  therefore  given  to  the  danger  of  injury  by  spraying 
while  the  trees  were  in  bloom.  The  blossoming  dates  for  1902  of  the 
various  varieties  of  peaches  grown  in  large  quantities  in  the  Placer 
County  district  are  given  in  the  following  table.  The  varieties  are 
arranged  in  approximately  their  ripening  order: 

Blossoming  Periods  of  Peaches. 

Variety.  First  Blossoms.  Full  Blossoms. 

Alexander March  15  March  20 

Hale... .- March  15  March  20 

Triumph March  16  March  2L 

Imperial Feb.      25  March    2 

St.  John Feb.      24  March    1 

Early  Crawford March  10  March  15 

Foster March    5  March  12 

Susquehanna March    5  March  12 

McDevitt _. March    2  March    8 

Levi .-  ... .. March  13  March  18 

Salvvay ...... March  15  March  20 

The  large  experiment  was  with  one  lot  of  some  two  hundred  Hale 
trees  at  the  Newcastle  station,  which  were  sprayed  with  the  lime,  salt 
and  sulfur  compound  on  March  17th  and  18th,  just  as  the  trees  were 
nearing  the  period  of  full  bloom. 

This  is  a  variety  that  exhibits  a  strong  tendency  to  drop  the  buds  in 
the  spring,  yet  the  trees  that  were  sprayed  when  in  blossom  set  fruit 
quite  as  freely  as  the  unsprayed  check  trees  in  the  neighborhood,  and 
also  as  did  the  trees  that  were  sprayed  earlier  in  the  season. 

Of  course,  some  blossoms  were  injured  by  this  treatment,  but  abso- 
lutely no  commercial  damage  was  done,  and  the  fruit  on  these  trees  was 
evenly  distributed  and  had  to  be  thinned.  The  injury  to  blossoms 
apparently  occurred  only  when  a  fully  open  blossom  stood  in  such  a 
position  as  to  be  filled  by  the  spray  and  to  retain  this  material  in  the 
cup.  This  combination  of  conditions,  however,  existed  in  so  few  cases 
that  the  number  of  blossoms  that  were  killed  by  the  spray  was  exceed- 
ingly small.  A  tree  will  have  blossoms  in  all  conditions  from  the 
swelling  bud  to  the  fully  open  flower,  and  if  the  latter  had  been  all  killed 
it  is  possible  that  there  might  be  no  real  loss. 

The  effect  of  the  atmospheric  conditions  was  seen  very  clearly  in  a 
portion  of  this  experiment.  During  a  few  hours  of  the  time  when  this 
work  was  being  done  the  atmosphere  became  extremely  dry,  because  of 
a  north  wind.  The  trees  sprayed  during  this  time  lost  a  much  larger 
number  of  blossoms,  and  tender  twigs  were  also  killed.  No  damage, 
however,  occurred  when  the  usual  moist  atmospheric  conditions  of  this 
season  of  the  year  prevailed.  Our  experience  this  season  has  indicated 
that  the  blossom  of  this  variety  of  peach  is  more  susceptible  to  injury  by 


peach-worm:  spring  control  measures. 


17 


spraying  than  is  the  case  with  any  other;  and  only  during  the  time 
drying  winds  are  blowing  need  there  be  any  hesitancy  in  spraying,  even 
though  the  tree  is  in  bloom. 

The  latest  spraying  in  the  experimental  orchards  on  Early  Crawfords 
was  March  5th  and  7th,  a  few  days  before  the  first  blossoms  appeared, 
but  after  the  buds  were  beginning  to  burst.  No  trace  of  injury  was 
observed.  Some  Fosters  were  sprayed  on  March  1st,  and  others  on 
March  5th  and  7th.  On  the  latter  date,  one  of  the  trees  that  was  nearly 
in  full  bloom,  -having  a  large  number  of  fully  opened  flowers  on  it, 
was  sprayed  with  especial  pains  and  thoroughness,  completely  drench- 
ing it  with  the  spraying  material,  in  order  to  produce  injury,  if  possible. 
A  careful  watch  was  kept  of  this  tree,  and  the  actual  loss  to  it,  so  far  as 
could  be  made  out,  was  eleven  blossoms.  The  tree  in  question  is  four- 
teen  years  old,  and  had  many  hundreds  of  blossoms  out  when  the 


Fig.  6.    Fruit  from  thinning  of  Foster  tree  sprayed  when  in  full  bloom. 

spraying  was  done.  So  much  fruit  set  on  this  tree  that  heavy  thinning- 
out  had  to  be  done  late  in  April,  when  1,635  peaches  were  taken  from 
it,  leaving  still  a  good  crop  on  the  tree.     (See  Fig.  6.) 

A  number  of  Susquehanna  trees  were  sprayed  on  March  12th,  13th, 
and  14th,  just  when  they  were  in  full  bloom;  no  apparent  damage 
was  done  to  the  flowers,  and  the  fruit  required  very  heavy  thinning. 

Spraying  was  done  on  a  number  of  the  McDevitts  on  the  11th  of 
March,  after  some  of  the  blossoms  had  fallen,  and  again  no  damage 
was  done. 

These  experiments  were  practically  duplicated  in  many  different 
orchards,  and  the  same  results  were  obtained  in  each  case.  It  can  thus 
be  safely  said  that  late  spraying  with  lime,  salt  and  sulfur,  under  the 
conditions  obtaining  in  Placer  County,  does  not  in  any  appreciable  way 


2— Bul.  144 


18  UNIVERSITY    OF   CALIFORNIA EXPERIMENT    STATION. 

affect  the  crop,  provided  the  spraying  is  not  done  when  the  atmosphere 
is  extremely  dry. 

Our  work  with  oils  and  emulsions  began  on  March  31st,  when  the  trees 
had  begun  to  set  fruit  and  most  of  the  blossoms  had  fallen.  Enough  of 
these  remained,  however,  for  us  to  see  the  effect  of  the  materials  used  on 
the  flowers,  and  some  slight  loss  of  fruit  through  burning  of  the  blos- 
soms was  shown.  This  burning  was  quite  as  evident  when  the  emul- 
sions were  used  as  weak  as  one  part  of  the  emulsion  to  fourteen  of  water 
as  when  the  distillate  oil  was  used  in  the  proportion  of  one  of  the  oil  to 
three  of  water.  Altogether  one  hundred  and  sixty-eight  Salway  peach 
trees  were  sprayed  with  these  materials. 

We  also  experimented  with  the  so-called  Hercules  emulsion  of  28° 
distillate  oil,  spraying  fourteen  Salwa)'  peach  trees  on  March  22d  with 
this  preparation,  used  in  the  proportion  of  one  to  ten  of  water.  At  this 
time  the  trees  were  just  past  full  bloom,  and  the  spraying  resulted  in 
considerable  loss,  on  account  of  the  blossoms  being  scorched.  Fully 
one  fifth  of  the  blossoms  on  these  trees  were  destroyed  by  the  spray. 

SPRING    HISTORY    OF   THE    WORM. 

As  the  spring  opened  it  became  possible  to  follow  the  beginning  of  the 
spring  activity  as  it  occurred  in  the  orchard  under  normal  conditions. 

The  worms  remained  inactive  in  their  burrows  until  early  in  March, 
when  they  began  to  work  their  way  out. 

Escape  from  Burrow. — The  process  of  leaving  the  burrow  was  observed 
very  continuously  during  this  time  in  the  breeding-cages,  where  twigs 
containing  hibernating  larvao  were  placed  with  their  ends  in  moist  sand; 
on  the  net-covered  tree,  where  one  hundred  and  thirty-five  worms  were 
under  observation;  and  also  in  the  orchard  trees,  where  perfectly  natural 
conditions  were  found.  These  three  sets  of  observations  gave  results 
that  tallied  in  all  particulars.  It  was  found  that  when  the  warm- 
weather  conditions  had  prevailed  to  a  sufficient  extent  to  make  the  sap 
begin  to  flow  appreciably  in  the  tree,  then  the  worms  also  became  active 
and  began  to  work  their  way  out  of  their  winter  burrows. 

Their  first  efforts  to  obtain  this  end  consisted  in  a  tearing  away  of 
the  silk  lining  of  the  burrows.  This  tearing-away  process  began  with 
the  removal  of  the  floor  portion  of  the  lining,  and  continued  until  about 
two  thirds  of  the  covering  portion  had  been  removed.  While  doing  this 
the  worms  first  fed  on  the  tender  tissues  of  the  bark  beneath  the 
original  burrow,  but  after  a  few  days  they  began  to  eat  their  way 
toward  the  surface,  filling  the  burrows  behind  them  with  excrement. 
They  usually  reached  the  surface  in  from  ten  days  to  two  weeks. 
During  this  time  a  considerable  increase  in  size  could  be  seen,  and  also 
a  marked  change  in  color,  the  worms  becoming  of  a  much  darker  shade. 


peach-worm:  spring  history. 


19 


Attack  on  Buds. — The  worms  when  they  appeared  on  the  surface  were 
from  3  to  4  millimeters  in  length.  These  worms  spent  the  first  two  or 
three  days  after  leaving  their  burrows  wandering  about  on  the  bark  of 
the  tree.  They  then  attacked  the  young  growth  and  bored  their  way 
into  the  pith  of  the  starting  bud,  either  from  the  side  or  at  the  tip,  the 
latter  being  the  point  most  generally  chosen. 

Frequently  the  worms  contented  themselves  with  merely  boring  into 
the  pith  from  the  side  and  then  withdrawing  and  attacking  some  other 
shoot.  The  twig  so  attacked  was  so  weakened  at  the  point  where  entry 
was  made  that  the  portion  above  the  wound  soon  died  away.  One  worm 
might  attack  many  buds  in  this  way  and  the  injury  to  the  tree  be 
multiplied.  The  worm,  again,  frequently  bored  its  way  into  the  pith  of 
the  chosen  shoot  and  then  took  a  downward  course,  eating  away  all  of 


Fig.  7.    Wilting  following  attack  of  bud- worm. 


Fig.  8.  Section  of  twig,  show- 
ing burrow  made  by 
bud-worm. 


the  twig  save  a  mere  shell  of  bark  and  fibrous  material  on  the  outside 
of  its  burrow.  This  burrow  was  partly  filled  with  excrement,  but  at 
no  time  did  we  find  a  burrow  sufficiently  filled  with  voided  material  to 
interfere  with  the  ready  passage  of  the  worm  up  or  down.  The  worms 
might  attack  a  number  of  twigs  in  this  way,  and  here  also  the  injury 
that  a  single  worm  might  do  was  multiplied.  The  twig  that  is  attacked 
very  quickly  wilts  and  dies,  and  this  wilted  appearance  of  the  twigs  is 
a  good  indication  of  the  presence  of  the  worm  at  work  in  the  tree. 
Indeed,  the  work  done  by  the  worm  at  this  time  and  the  after-appear- 
ance of  the  twig  are  quite  characteristic  and  easily  recognized.  In  Fig.  7 
is  given  a  good  illustration  of  this  work  of  the  " bud-worm,"  as  the 
creature  is  known  in  this  stage  of  its  life,  and  the  wilted  appearance  of 
three  or  four  leaves  above  the  point  where  the  worm  is  at  work  can  be 
seen.  Fig.  8  shows  a  section  of  a  newly-started  twig,  down  which  a 
worm  had  burrowed  its  way  until  it  had  reached  the  old  and  hard  wood. 


20  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

Again,  in  Fig.  9  can  be  seen  a  photograph  of,  first,  a  twig  which  had 
not  been  attacked  at  any  time  by  the  "bud-worm,"  and  then  of  several 
on  which  the  attack  was  very  severe.  It  will  be  seen  from  these  illus- 
trations that  the  work  of  the  "bud-worm"  may  result  in  very  serious 
consequences  to  the  tree  as  well  as  to  the  crop,  if  not  actually  threat- 
ening the  very  existence  of  the  tree  itself.  In  many  instances  of  the 
bud-worm  work  that  came  under  observation  this  season,  the  tree 
appeared  as  though  burned  by  fire. 

The  attack  of  the  bud-worm  is  generally  more  to  be  noticed  and 
feared  on  young  trees  than  on  older  ones.  We  have  found  that  three  or 
four  worms  could  completely  destroy  a  three-year-old  tree,  and  while 
this  attack  on  an  older  tree  would  be  serious,  yet  it  would  not  be  fatal. 


\ 

K  i 

I     |v/Pf         IB?                ft            'U:             <     ^ 

Jm  f  WJ^'i,        *\0'*          wi      f  it 

1*$  }  t'tfa 

k  T 

Fig.  9.    Results  of  bud-worm  attack,  shown  in  the  six  twigs  on  right.    Left-hand 
twig  has  not  been  attacked. 

The  most  serious   work    of    this  kind   is  in    newly-placed  grafts   and 
dormant  buds,  which  are  very  frequently  attacked  and  destroyed. 

The  work  of  the  worms  in  the  buds  and  new  twigs  continued  until 
pupation  was  first  observed  in  the  latter  part  of  April.  The  full-grown 
larvse  at  this  time  were  about  10  millimeters  in  length  and  the  general 
color  quite  dark,  the  characteristics  as  shown  by  the  young  larvae 
remaining  almost  unchanged. 

RESULTS    ON    BUD-WORM    OF    EARLIER    WORK. 

Our  first  comparisons  of  the  effect  of  the  spraying  experiments  were 
made  possible  when  the  bud-worm  work  began  to  be  evident,  which  was 
in  the  latter  part  of  March  and  early  in  April.  At  this  time  it  was 
found  that  the  worms  were  very  plentiful  all  over  the  district  on  such 
trees  as  had  not  been  sprayed  at  all.     From  one  of  our  check-trees  at 


peach- worm:  spring  control  measures.  21 

the  Newcastle  station  we  cut  out  eighteen  bud-worms,  and  the  average 
number  on  some  forty  un sprayed  trees  on  this  place  was  eleven  worms. 
The  same  heavy  infestation  was  shown  at  the  Ophir  station  also,  while 
from  one  unsprayed  tree  at  station  A  we  removed  twenty-three  bud- 
worms.  Check-trees  at  stations  B  and  C  were  also  badly  infested ; 
while  the  unsprayed  orchards  generally  were  infested  at  the  rate  of 
from  two  to  ten  worms  to  the  tree.  The  number  of  bud-worms  found 
on  the  check-trees  through  the  whole  district  indicated  that  the  season 
was  a  favorable  one  for  the  peach-worm. 

On  sprayed  trees,  using  the  same  bud-worm  basis  of  computation,  we 
found  that  where  the  IX L  compound  had  been  used  no  control  of  the 
worm  whatever  had  been  obtained.  The  trees  on  places  2,  3,  4,  5,  and 
6  were  as  badly  infested  with  the  bud-worm  as  though  no  spray  at  all 
had  been  used,  and  from  five  to  twelve  worms  were  cut  from  many  of 
the  trees  on  these  places.  Some  of  the  trees,  and  this  especially  on 
place  No.  6,  appeared  as  though  burned,  as  the  result  of  the  work  of  the 
bud-worm.  No  " curl-leaf"  was  noted  among  these  trees,  and  their 
general  condition,  other  than  the  effect  of  the  bud-worms,  was  fair. 

The  trees  which  had  been  sprayed  with  the  distillate  oils  and  emul- 
sions showed  a  very  much  lighter  attack  of  the  bud-worms,  for  among 
these  trees  it  was  found  that  the  average  number  of  bud-worms  was 
from  one  to  two  to  the  tree;  while  from  the  check-trees,  unsprayed,  on 
the  same  orchard,  we  cut  from  eight  to  twelve  bud-worms.  These  oil- 
sprayed  trees  were  affected  with  "curl-leaf"  quite  severely. 

The  lime-salt-and-sulfur-sprayed  trees,  when  the  spraying  had  been 
done  in  the  early  spring,  showed  the  most  satisfactory  results  of  any  at 
this  time.  On  the  various  station  orchards,  comprising  over  12,000 
peach  trees,  the  average  number  of  bud-worms  was  about  one  to  every 
ten  trees,  and  this  average  was  maintained  on  many  other  orchards  in 
the  district.  Indeed,  it  was  a  difficult  matter  to  find  the  worms  in  these 
orchards,  and  it  was  only  by  the  closest  scrutiny  of  the  trees  that  they 
could  be  located  in  them.  The  general  condition  of  these  trees  was 
excellent  and  a  marked  absence  of  "  curl-leaf"  was  noted. 

An  examination  of  the  trees  in  orchard  No.  1,  that  had  been  sprayed 
with  the  lime,  salt  and  sulfur  early  in  February,  showed  that  the  attack 
by  bud-worms  was  severe.  On  many  of  the  trees  from  which  we  cut 
the  worms  we  found  from  five  to  nine  to  the  tree.  The  general  condi- 
tion of  the  trees  was  good  and  a  very  small  amount  of  "  curl-leaf"  was 
present. 

Winter  spraying  with  the  Hercules  distillate  emulsion  in  February  at 
the  Ophir  station  also  resulted  in  leaving  the  bud-worms  in  dangerous 
numbers.  The  trees  of  the  kerosene  emulsion  and  the  kerosene  oil  and 
water  experiments  at  the  Newcastle  station,  which  had  been  winter- 
sprayed,  showed  also  heavy  infestation.     Indeed,  the  condition  of  these 


22 


UNIVERSITY    OF   CALIFORNIA — EXPERIMENT    STATION. 


trees  was  so  bad  that,  fearing  the  moths  might  spread  from  them  to  the 
balance  of  the  orchard,  all  the  bud-worms  were  cut  from  the  twigs. 
The  following  table  gives  this  work  and  its  result  in  detail : 


Table  Showing  Bud-Worms  on  Winter-Sprayed  and  Unsprayed  Trees. 


Variety. 

Hale 

Hale 

Hale 
Salway 
Salway 
Salway 


Spray  Used  in  Winter. 

Kerosene  emulsion  1  part,  water  8  parts.. 
Kerosene  emulsion  1  part,  water  10  parts. 

Kerosene  1  part,  water  3  parts 

Kerosene  emulsion  1  part,  water  8  parts .. 
Kerosene  emulsion  1  part,  water  10  parts. 
Kerosene  1  part,  water  3  parts 


Bud-Worms 
Removed  from 
Sprayed  Trees. 

Bud-Worms  on 

Unsprayed 

Check-Trees. 

19 

20 

21 

20 

18 

20 

17 

16 

19 

16 

22 

16 

The  Pupa. — The  pupa  or  chrysalis  of  the  peach-moth,  shown  in  Fig.  10, 
varies  from  light  to  dark  yellow  in  color.     It  is  from  5  to  7  millimeters 

long,  and  is  rather  broad  in 
comparison  with  its  length. 
The  segments  of  the  abdomen 
are  well  defined,  but  only  the 
last  three  are  movable,  allow- 
ing a  certain  small  amount 
of  movement  of  a  twitching 
nature.  The  eye  spots  are  of 
a  darker  color  than  the  rest 
of  the  pupa,  and  are  quite 
prominent. 

Pupation. —  The  worms 
having  attained  their  full 
growth,  withdrew  from  the 
green  material  in  which  they 
had  been  working  and  crawled 
down  the  limbs  to  the  main 
branches  and  to  the  trunk. 
Here  the  rough  bark  offered 
many  places  of  scanty  concealment  sufficient  for  pupation.  The 
worm,  in  at  least  the  greatest  number  of  cases,  chose  for  this  purpose 
the  hollow  formed  by  the  curling-up  of  small  portions  of  the  outer 
bark.  These  "curls"  of  the  bark  are  quite  characteristic  of  the  peach 
tree  and  are  constantly  present  on  the  trunk  and  larger  branches.  The 
worms,  after  crawling  into  these  curls,  wreave  an  extremely  loose  cocoon — 
a  few  threads  of  whitish  silk  drawn  irregularly  across  the  open  portion 
of  the  curl,  and  a  slight  silken  carpet,  to  which  the  hooks  at  the  end  of 
the  abdomen  of  the  pupa  are  attached,  constituting  the  whole  structure. 
As  far  as  our  observations  go  this  is  always  the  method  of  cocoon- 
making.     This  cocoon  merely  serves  to  hold  the  pupa  in  place,  and  does 


Fig.  10.    The  pupa.    Dorsal  and  ventral  views. 


peach-worm:  spring  control  measures. 


23 


not  in  any  other  way  serve  to  protect  it.  In  ninety-two  per  cent  of  the 
cases  noted  the  position  was  well  down  on  the  trunk  of  the  tree.  In  a 
very  few  cases  the  worms  pupated  in  the  " curls"  of  the  bark  quite  well 
up  in  the  tree,  and  in  only 
three  per  cent  of  the  cases 
noted  did  pupation  take 
place  under  broken  places  in 
the  bark  where  there  is  no 
evident  curl.  After  choosing 
their  pupation  places  and 
spinning  their  slight,  web- 
like cocoons,  the  worms  pro- 
ceeded to  pass  into  the  pupa 
form,  attaining  it  in  from  two 
to  two  and  a  half  days. 
Fig.  11  shows  the  pupation 
place  and  the  cocoon. 

CAMPAIGN    AGAINST    THE  PUPA. 


Two  points  in  this  matter 
of  pupation  seem  of  economic 
importance,  and  were  made 
the  basis  of  some  of  our  ex- 
periments for   the  Control   of  FlG'U-    Potion  place  and  cocoon. 

the  worm.  Unlike  the  codling- moth  larva,  peach-worms  crawl  down 
the  tree  to  the  trunk,  and  do  not  drop  to  the  ground  and  then  crawl  to 
the  tree.  Secondly,  the  large  majority  of  the  worms  pupate  on  the 
main  trunk  of  the  tree. 

These  experiments  consisted  of  the  use  of  band  traps,  and  of  oil  spray 
on  the  trunk. 

Band  Traps. — Since  the  use  of  bands  as  an  adjunct  to  spraying  opera- 
tions in  certain  cases  against  the  codling-moth  is  generally  recognized 
as  effective,  it  was  thought  by  ourselves  and  by  some  growers  that  these 
devices  might  be  of  more  or  less  value  in  the  case  of  this  insect,  and 
that  it  was  important  to  test  what  value  they  might  have.  To  deter- 
mine this  point,  the  following  experiments  were  made:  On  April  15th, 
pieces  of  "sticky  fly  paper"  were  placed  on  the  ground  close  about  the 
trunk  of  a  peach  tree,  in  such  a  way  that  a  worm  coming  to  the  tree 
would  have  to  cross  the  paper  to  get  on  the  trunk.  Eleven  days  later 
there  were  seven  pupae  taken  from  the  trunk  of  this  tree  and  not  a 
worm  had  been  taken  on  the  paper.  On  April  16th  paper  was  placed 
in  the  same  way  about  another  tree,  and  fourteen  days  later  twelve 
pupse  were  taken  from  the  trunk  of  this  tree,  but  not  one  worm  was  on 


24  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

the  paper.  On  the  4th  of  April  bands  of  burlap  were  put  about  the 
trunks  and  larger  limbs  of  five  trees.  These  trees  and  the  bands  were 
carefully  examined  from  time  to  time,  and  four  of  these  trees  yielded 
seven  pupae  apiece,  yet  not  one  of  these  was  found  beneath  a  band. 
They  were  all  placed  within  the  "curls"  of  the  bark,  as  described  above, 
and  on  the  main  trunk  of  the  tree.  Some  were  above  and  some  below 
the  band  on  the  trunk.  On  the  fifth  tree  one  pupa  out  of  eight  was 
beneath  the  trunk  band,  but  in  a  "curl"  of  the  bark.  Paper  bands 
were  used,  with  the  same  result  as  when  the  burlap  was  used.  "Sticky 
paper"  was  used  as  a  band  in  one  case  in  this  generation.  This  paper 
was  placed  about  the  trunk  just  where  the  branches  began,  and  on  this 
paper  two  worms  were  taken.  Seven  pupae  were  taken  in  a  space  of 
six  inches  above  this  band  and  none  below  it. 

Furthermore,  we  have  observed  in  four  different  instances  the  full 
process  of  pupation  in  this  generation,  and  in  every  instance  the  worm 
crawled  down  the  tree  from  the  green  twigs  (where  it  had  been  eating) 
to  the  main  trunk,  entered  one  of  the  "curls"  of  the  bark,  and  there 
went  through  the  process.  In  no  case  observed  did  the  worm  drop  to 
the  ground  and  then  make  its  way  to  and  up  the  trunk  of  the  tree,  and 
from  our  observations  and  from  the  results  obtained  from  our  "sticky 
paper"  and  band  experiments,  we  should  consider  that  such  a  proceed- 
ing seldom  or  never  occurs.  We  could  find  no  warrant  for  the  use  of 
band  traps  in  the  campaign  against  the  peach-worm. 

Oil  Spraying. — Early  in  May  the  conditions  existing  on  place  No.  2, 
which  is  noted  as  having  been  sprayed  with  the  I  X  L  compound,  were 
very  bad.  The  attack  of  the  bud-worm  was  severe  on  this  orchard,  and 
at  the  time  noted  these  worms  had  begun  to  pupate.  The  pupae  seemed 
to  be  quite  accessible  to  sprays  in  their  slight  cocoons  on  the  trunk  and 
larger  branches,  and  we  determined,  with  the  assistance  of  the  owner, 
to  see  what  effect  spraying  with  kerosene-oil  and  distillate-oil  emulsions 
would  have  on  these  pupae.  On  May  15th  and  16th,  after  a  few  moths 
had  emerged,  but  while  most  were  still  in  the  pupa  form,  we  sprayed 
these  trees.  The  emulsions  were  made  up  of  the  28°  and  33°  distillate 
and  with  150°  kerosene  oil.  These  emulsions  were  diluted  with  water 
in  the  proportion  of  one  to  eight,  and  this  material  was  thoroughly 
sprayed  over  the  trunks  and  larger  branches  of  the  trees.  Care  was 
taken  not  to  spray  the  material  on  the  leaves  and  new  growth,  yet  some 
of  it  did  lodge  in  such  positions.  Where  this  occurred  the  leaves  and 
twigs  were  badly  discolored  (yellowed),  but  in  a  few  weeks  they  regained 
their  normal  color  and  health.  This  discoloration  occurred  quite  as 
much  in  the  case  of  the  kerosene  emulsion  as  in  that  of  the  distillate- 
oil  emulsion.  Two  days  after  this  spraying  was  done  we  removed  a 
number  of  the  pupae  from  the  trees  and  kept  them  under  observation 


peach-worm:  spring  control  measures.  25 

for  four  weeks.  Moths  emerged  from  two  of  the  twenty  pupae  so  kept, 
the  rest  having  been  killed  by  the  spray.  The  ultimate  results  of  this 
treatment,  as  shown  by  the  percentage  of  wormy  fruit,  will  be  seen  in 
the  discussion  of  that  subject  below. 

THE    MOTH. 

The  adult  moths  began  to  emerge  from  the  pupae  in  from  ten  to 
twelve  days.  They  are  of  small  size,  very  delicate,  with  narrow,  well- 
fringed  wings.  The  color  is  quite  subdued,  being  a  beautiful  dark 
steel-gray  in  general  effect.  On  closer  examination  it  will  be  noticed 
that  this  general  color  is  relieved  by  certain  darker  spots  on  the  fore 
wings,  which  are  folded  over  the  abdomen  when  the  insect  is  at  rest. 
The  palpi  are  quite  prominent  and  are  usually  bent  back  over  the 
insect's  head,  having  the  appearance  of  horns.  The  antennae  are  very 
delicate,  of  a  grayish  color,  ringed  with  brown,  and  are  laid  on  the 
wings  when  the  moth  is  at  rest.  The  hind  wings  are  much  lighter  in 
color  and  more  heavily  fringed  than  the  fore  wings,  and  both  pairs  of 
wings  seem  under  the  magnifying  glass  to  be  dusted  over  with  a  grayish 
powder.  The  length  of  the  moth  when  at  rest  is  about  7  m.m.,  and  with 
wings  expanded  the  insect  measures  14  m.m.  from  tip  to  tip.  It  differs 
from  other  members  of  the  group  in  certain  minute  particulars  not  easy 
to  specify.  These  other  moths  are  not  likely  to  be  found  in  the  same 
situations,  so  that  the  above  description  will  enable  one  to  be  fairly  cer- 
tain of  their  identity. 

The  moths  are  very  quick  in  their  movements  and  are  easily  dis- 
turbed, flying  rapidly  from  one  place  of  concealment  to  another  in  the 
orchard. 

Lantern  Traps. — The  value  of  lantern  traps  in  the  war  against  the 
related  potato-worm,  reported  in  Bulletin  No.  135  of  this  Station,  sug- 
gested their  use  in  this  case  also.  The  traps  were  therefore  thoroughly 
tested  during  May,  when  the  moths  were  on  the  wing.  A  number  of 
lantern  traps  made  after  the  Colorado  type*  were  used.  These  traps 
consist  of  a  piece  of  bright  tin  made  into  a  funnel  shape  and 
opening  into  a  wooden  bottle.  In  this  bottle  is  placed  a  piece  of 
cyanide  of  potassium  wrapped  in  paper.  Over  this  a  little  excelsior 
(wood  shavings  packing)  is  placed.  When  in  use  the  trap  is  hung 
to  some  tree  in  the  orchard,  a  lantern  is  hung  just  above  it,  and 
the  poison  bottle  is  slipped  over  the  bottom  opening  of  the  funnel. 
Insects  attracted  by  the  light  readily  find  their  way  into  the  funnel  and 
then  into  the  poison  bottle.  Beetles  taken  thus  crawl  into  the  loose 
packing  in  the  bottle  and  do  not  injure  the  more  delicate  insects  which 
may  be  taken  and  which  remain  on  top.     Many  specimens  of  various 


Bulletin  43,  Colorado  Experiment  Station. 


26 


UNIVERSITY    OF    CALIFORNIA —EXPERIMENT    STATION. 


genera  of  beetles  were  taken,  and  some  moths,  a  few  parasitic  hymenop- 
tera,  and  many  mosquitoes  (Culex  and  Anopheles  sp.)  were  victims  of 
these  traps,  but  we  looked  in  vain  for  the  peach-moth.  Not  a  single 
peach-moth  was  taken  by  these  traps  during  the  experiment,  in  spite  of 
the  fact  that  they  were  present  in  numbers  in  the  orchards. 


EGG-LAYING. 

The  moths  began  egg  laying  on  May  9th.  The  newly-placed  egg  is 
pearly  white,  and  shows  under  the  microscope  a  rather  coarse  reticula- 
tion.    Before  hatching  the  color  changes  to  a  deep  yellow,  almost  orange 

color,  and  at  this  stage  the  egg  is 
quite  conspicuous.  It  is  about  two 
fifths  of  a  millimeter  in  length  by 
one  fifth  in  breadth,  being  a  rather 
long  oval  in  shape,  about  twice  as 
long  as  broad. 

These  eggs  were  generally  placed 
in  the  new  twigs  near  the  bases  of 
the  leaves,  and  from  one  half  to  two 
thirds  of  the  distance  out  from  the 
point  of  beginning  of  the  twigs. 
The  eggs  were  placed  lengthwise  of 
the  twigs,  and  in  a  few  cases  were 
concealed  beneath  the  bracts  at  the 
bases  of  the  leaves.  We  could,  how- 
ever, note  no  general  attempt  at  con- 
cealment of  the  eggs  under  these 
bracts  or  spurs,  as  is  recorded  by 
Marlatt  (Bulletin  10,  n.  s.,  U.  S. 
Dept.  of  Agric,  Div.  of  Entomology, 
p.  13),  and  they  were  as  a  rule 
plainly  to  be  seen.  The  illustration 
(Fig.  12)  shows  the  general  distribution  of  the  eggs  in  the  neighborhood 
of  leaf  bases,  some  eggs  being  laid  singly  and  some  in  loose  clusters. 
They  are  rather  insecurely  glued  to  the  surface  of  the  twig. 


Fig  12.    Eggs  of  Peach-moth  in  position 
on  twig. 


WORMS    OF   THE    SECOND    GENERATION. 

Young  worms  began  to  come  from  these  eggs  on  as  early  as  May  19th, 
the  period  of  incubation  being  about  ten  days.  The  newly-hatched 
larvae  were  about  three  fourths  of  a  millimeter  in  length,  and  did  not 
differ  in  general  appearance  from  the  hibernating  worms  asfiescribed  on 
a  previous  page. 

These  worms  were  restless  for  the  first  two  or  three  days  of  their  lives, 
wandering  about  on  the  twigs  and  apparently  doing  scarcely  any  eating. 


peach-worm:  second  generation.  27 

Finally  they  would  select  a  place  a  short  distance  from  the  tip  of  the 
twig  and  eat  into  it  at  the  base  of  a  leaf,  bore  into  the  pith,  and  then 
follow  down  the  pith  in  the  same  manner  as  the  first  generation  of 
worms  did.  This  boring  process  was  not  observed  in  any  case  to  extend 
down  the  twig  more  than  an  inch,  and  the  same  worm  would  attack 
many  twigs.  Frequently,  also,  as  in  the  first  generation,  the  worm 
would  merely  bite  into  the  twig  a  short  distance  and  then  withdraw, 
not  having  reached  the  pith.  In  either  case,  however,  the  apparent 
damage  was  the  same,  as  the  twig  died  above  the  point  of  attack,  and 
some  bud  below  the  injury  would  have  to  be  forced  out  to  take  the  place 
of  the  terminal  bud,  in  order  to  continue  the  growth  of  the  twig.  This 
dying-back  being  entirely  at  the  ends  of  the  twigs,  and  the  leaves  soon 
drying  to  a  pale  yellow,  rendered  this  injury  quite  evident.  (See  Fig.  7.) 
The  worms  act  thus  as  "twig-borers"  for  a  period  covering  about 
twenty  days,  and  then  seek  the  fruit,  if  any  is  on  the  tree.  If  there  is 
no  fruit  on  the  tree,  then  the  whole  life  of  the  worm  will  be  spent  as  a 
"  twig-borer,"  and  the  damage  of  this  kind  becomes  all  the  more  evident. 

Attempt  to  Poison  these  Worms. — Reports  of  success  by  the  use  of  Paris 
green  against  the  bud-worm  indicated  a  possible  means  of  control.  The 
experimental  work  was  done  when  the  worms  of  the  second  generation 
had  begun  to  appear,  which  was  about  May  19th,  and  the  poison  used 
was  from  samples  furnished  by  the  Station  laboratory  at  Berkeley. 
These  samples  are  designated  as  Nos.  610  and  611,  and  the  following 
tables  give  the  method  of  work  and  results  obtained  from  their  use.  The 
mixtures  in  all  cases  were. made  up  with  lime  in  the  proportion  of  5 
pounds  to  100  gallons  of  water.  The  lime  was  first  slaked  and  a  milk 
of  lime  made,  and  this  mixture  was  strained  to  remove  lumps  and  grit. 
The  desired  amount  of  Paris  green  was  then  made  into  a  paste  with 
water,  and  added  to  the  lime  water  in  the  proportion  being  experimented 
with.  The  atmospheric  moisture  was  determined  by  a  device  consisting 
of  a  string  six  feet  long,  hung  in  such  a  way  that,  while  the  air  had  full 
play  upon  it,  it  was  in  the  shade  at  all  times  and  no  wind  blew  upon  it. 
A  light  weight  was  hung  to  the  end  of  this  string.  The  string  would 
shrink  up  when  the  atmosphere  was  humid,  and  regain  its  normal  length 
under  dry  conditions.  This  method  gave  us  the  comparative  humidity 
only,  but  this  was  enough  for  the  purpose. 


28 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


Table  of  Expekiments  with  Paris  Green,  Sample  No.  610. 


Pr0Used.°nS  When  APPlied- 
1-800        May  20,    7  a.  m. 

May  20,  11  a.  m. 
"  May  20,    2  p.m. 

"  May  20,    6  p.  m. 

"  May  27,    7  a.  m. 

May  27,  11  a.m. 

May  27,    2  p.  m. 

May  27,    6  p.m. 

1-1600      May  22,    7  a.  m. 

"  May  22,  11  a.  m. 

May  22,    2  p.  m. 
"  May  22,    6  p.m. 

May  29,    7  a.m. 

May  29,  11  a.m. 
"  May  29,    2  p.  m. 

May  29,    6  p.m. 


Atmospheric 
Humidity. 

High 

Medium 

Low 

Low 

Mod't'ly  high 

Below  medium 

Low 

Very  low 

High 

Medium 

Low 

Very  low 

Mod't'ly  high 

Below  medium 

Low 

Very  low 


Condition  of 
Leaves. 
Turgid 
Turgid 
Wilted 
Wilted 
Turgid 

Sl'tly  wilted 
Wilted 

Much  wilted 
Turgid 
Turgid 
Wilted 

Much  wilted 
Turgid 

Sl'tly  wilted 
Wilted 

Much  wilted 


Injury  to 
Leaves. 
Slight 
Some 
Much 
Much 
Some 
Some 
Much 
Much 
Some 
Some 
Much 
Much 
Slight 
Some 
Some 
Much 


Injury  to 

Fruit. 

No  fruit 

No  fruit 

No  fruit 

No  fruit 

In  spots 

In  spots 

In  spots 

In  spots 

Some 

Some 

Some 

Some 

In  spots 

In  spots 

In  spots 

In  spots 


Table  of  Experiments  with  Paris  Green,  Sample  No.  611. 


1-800 


1-1600 


May  21, 
May  21, 
May  21, 
May  21, 
May  28, 
May  28, 
May  28, 
May  28, 
May  21, 
May  21, 
May  21, 
May  21, 
May  28, 
May  28, 
May  28, 
May  28, 


7  A.  M. 

11  A.  M. 

2  P.  M. 

6  P.  M. 

7  A.  M. 
11  A.  M. 

2  P.  M. 

6  P.  M. 

7  A.  M. 
11  A.  M. 

2  P.  M. 

6  P.  M. 

7  A.  M. 
11  A.  M. 

2  P.  M. 
6  P.  M. 


Very  high 
Medium 

Low 

Low 

High 
Medium 

Low 

Low 

Very  high 

Medium 

Low 

Low 

High 
Medium 

Low 

Low 


Turgid 
Turgid 
Wilted 
Wilted 
Turgid 
Turgid 
Wilted 
Wilted 
Turgid 
Turgid 
Wilted 
Wilted 
Turgid 
Turgid 
Wilted 
Wilted 


None 
Some 
Much 
Much 
Some 
Some 
Much 
.  Much 
Some 
Some 
Much 
Much 
Very  little 
Some 
Much 
Much 


Slight 
Slight 
Much 
Much 
Some 
Some 
Much 
Much 
In  spots 
In  spots 
Much 
Much 
Some 
Some 
Much 
Much 


It  will  be  seen  that,  so  far  as  the  apparent  injury  goes,  there  was  no 
material  difference  between  the  samples  used,  which  were  both  greens 
that  had  passed  the  California  test  and  were  good.  In  every  instance, 
save  one,  the  material  burned  the  foliage.  It  will  be  seen  from  the 
table  that  in  the  7  a.  m.  experiment  of  May  21st,  with  sample  No.  611, 
no  damage  was  apparent,  so  far  as  the  foliage  is  concerned,  and  only  a 
slight  burning  of  the  fruit.  Whatever  the  reason  for  this  exception,  the 
fact  remains  that,  under  the  conditions  most  commonly  obtained,  there 
was  more  or  less  damage  done  to  both  leaves  and  fruit  in  all  the  other 
experiments.  The  damage  consisted  in  the  entire  destruction  of  the 
leaves  in  some  cases,  in  the  destruction  of  the  pendent  portion  of  the 
leaves  where  a  drop  of  the  material  gathered  in  other  cases,  and  in  spots 
being  burned  in  the  leaves  in  still  others.  The  fruit  injury  consisted 
generally  in  the  burning-out  of  spots  upon  it;  and  these  spots  did  not 
develop,  but  either  gave  the  fruit  an  unsightly  appearance,  or  decay 
started  in  the  injured  place  and  the  fruit  rotted. 


peach- worm:  second  generation,  history.  29 

The  experiments  as  tabulated  were  paralleled  by  another  series,  in 
which  a  spray  of  water  was  used  before  the  Paris  green  mixture  was 
applied,  and  the  tree  well  moistened.  The  results  in  nowise  differed 
from  those  reported  above  in  detail,  which  were  sprayed  in  the  usual 
manner.  These  results  were  furthermore  confirmed  on  another  place  near 
the  Newcastle  station,  where  spraying  was  being  done  on  some  pear 
trees  with  Bordeaux  mixture  to  which  Paris  green  had  been  added  in 
the  proportion  of  one  pound  of  the  Paris  green  to  180  gallons  of  the 
latter.  Two  peach  trees,  four  years  old  and  in  full  foliage,  were,  by 
error  of  the  workmen,  sprayed  with  this  material.  The  result  was  that 
the  leaves  and  many  of  the  young  branches  were  killed  outright. 

The  experiments  with  the  Paris  green  were  carried  no  further,  as 
the  damage  done  to  the  trees  and  fruit  was  so  great  as  to  render  it 
certain  that  its  use  would  be  wholly  inadvisable  under  the  conditions 
existing  in  Placer  County. 

STUDY  OF  THE  FRUIT-WORM. 

Early  in  June  the  second  generation  of  worms  begins  operation  as 
fruit-worms.  They  had  been  working  some  time  as  twig-borers  as 
already  described,  but  for  some  unknown  reason  now  began  to  leave  the 
twigs  and  attack  the  fruit. 

It  is  in  this  work  in  the  fruit  that  the  insect  does  its  greatest  damage 
and  has  attracted  most  attention.  The  attack  on  the  fruit  is  very 
characteristic,  nothing  else  being  mistakable  for  it. 

The  worms  of  the  second  generation  on  leaving  the  twigs  bore  into 
the  peaches  at  the  stem  end  in  a  majority  of  cases.  Not  only  is  the  stem 
end  thus  generally  chosen  for  the  beginning  of  the  attack,  but  a  certain 
portion  of  the  stem  end — the  line  that  is  called  the  suture.  After 
boring  through  the  skin  the  worm  begins  to  feed  upon  the  tissue  of  the 
fruit  beneath,  often  excavating  a  large  chamber,  which  is  more  or  less 
filled  with  gummy  matter  and  excrement.  The  mouth  of  the  burrow  is 
also  generally  filled  with  these  materials  mixed  together. 

The  skin  above  the  hollowed-out  portion  of  the  fruit  first  turns  dark 
and  shrivels  up  to  a  certain  extent,  and  finally  decay  usually  sets  in. 
When  riper  fruit  is  attacked  the  worm  frequently  burrows  to  and  around 
the  pit;  and  if  the  latter  is  split  it  often  attacks  the  seed. 

The  worm  may,  under  certain  circumstances,  make  its  attack  at  other 
points  than  in  the  stem  end  of  the  fruit.  Quite  frequently  when  two 
peaches  are  in  contact  on  the  tree,  the  worm  bores  its  way  into  one  of 
the  fruits  at  this  point  of  contact;  or  if  a  leaf  or  twig  touches  the  fruit, 
here  also  the  worm  may  enter.  The  character  of  the  injury  is  the  same 
in  any  of  these  cases,  and  the  fruit  is  ruined. 


30 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


PUPATION. 

Early  in  July  the  most  precocious  worms  of  this  generation  begin 
to  withdraw  from  the  fruit  and  to  pupate,  and  this  coming-out  for 
pupation  continues  as  late  as  the  last  of  August  before  the  last  of  them 
have  completed  their  work.  The  position  chosen  for  pupation  is  in  the 
stem  end  of  the  fruit,  and  usually  not  the  one  in  which  the  worm  has 
been  working,  but  often  a  sound,  uninjured  one. 

The  worm  lays  itself  along  the  suture-hollow  in  the  stem  end  of  the 
peach,  and  fastens   itself   here   by  two   strands   of   silk,  making   less 


Fig.  13.    Pupse  of  the  second  generation  of  peach-worms  in  position  upon  the  fruit. 


attempt  at  a  cocoon  than  in  the  first  generation.  In  from  twenty-four 
to  forty-eight  hours  it  passes  into  the  pupa  form.  Though  this  is  the 
usual  place  and  method  of  pupation  in  this  generation,  there  are  a 
number  of  other  modes.  In  some  instances  the  worms  choose  a  space 
between  two  peaches  that  lie  close  together,  finding  here  a  satisfactory 
place  of  concealment.  In  a  few  cases  this  change  took  place  in  rough 
places  on  the  bark,  or  under  leaves  lying  against  small  branches  or 
twigs.  In  Fig.  13  will  be  seen  pupae  in  the  positions  chosen  by  the 
large  majority  of  the  worms  as  described  above. 

These  pupae  do  not  differ  in  any  way  from  those  produced  by  the  first 
or  winter  generation  of  worms. 


peach-worm:  third  generation.  31 


THE   MOTH    AND    EGG-LAYING. 


The  moths  issue  from  these  pupse  in  seven  days,  and  do  not  differ 
appreciably  from  those  of  the  spring  generation.  Egg-laying  began  on 
the  second  or  third  day  after  emer- 
gence, and  usually  continued  for 
three  days.  These  eggs,  which  are 
shown  much  magnified  in  Fig.  14, 
are  placed  on  the  edge  of  the  de- 
pression where  the  stem  is  attached 
to  the  fruit;  and  were  not,  in  any 
instance  noted,  placed  on  the.  twigs, 
as  are  the  eggs  from  the  moths  of 
the  other  generations.  The  eggs  are 
usually  placed  singly,  and  no  real 
grouping  of  them  was  seen,  though 
in  some   cases   two  or  three  were 

found     quite     close    together.      The     Fig.  14.    Eggs  of  the  second  generation  peach- 
fuzzineSS    SO    Characteristic    of    the       moth  in  position  on  fruit;  much  magnified. 

peach  seems  to  render  a  secure  fastening  of  these  eggs  impossible,  and 
they  could  be  easily  removed  from  their  position. 

WORMS   OF   THE   THIRD   GENERATION. 

The  young  worms  began  to  appear  on  the  sixth  day.  They  first 
wandered  about  on  the  surface  of  the  peaches  for  a  few  hours,  and  then 
ate  their  way  into  them  in  much  the  same  manner  as  the  worms  of  the 
second  generation.  The  worms  of  this  brood  are  the  only  ones  that  enter 
the  fruit  immediately  on  hatching.  They  make,  therefore,  at  first  very 
minute  burrows,  contrasting  strongly  with  freshly-made  burrows  of  the 
preceding  generation. 

FALL  HISTORY  OF  THE  INSECT. 

The  worms  of  this  generation  continue  their  work  in  the  fruit  for 
about  a  month,  when,  their  full  growth  having  been  reached,  they  come 
to  the  surface  to  pupate.  The  method  of  pupation  and  position  chosen 
for  this  purpose  differ  in  nowise  from  those  of  the  second  generation,  as 
described  above.  About  six  days  were  spent  in  the  pupa  form,  and  the 
moths  began  to  appear  about  the  middle  of  August. 

Egg-laying  began  in  the  latter  part  of  August  and  continued  well 
into  September.  These  eggs  were  placed  sometimes  in  small  cracks 
and  crannies  of  the  bark,  and  sometimes  quite  exposed  on  the  bark  of 
the  older  wood  just  above  the  crotches  formed  by  the  new  wood. 

The  eggs  hatch  in  about  five  days,  and  the  young  worms,  which 
are  from  one  half  to  three  fourths  of  a  millimeter  in  length,  immediately 


32 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


proceed  to  bore  into  the  bark  of  the  crotches  formed  by  the  new  wood 
with  the  growth  of  the  previous  year,  and  to  prepare  their  winter 
quarters.  In  the  region  under  investigation  hibernation  was  well 
begun  this  season  on  September  1st,  and  the  fully-made  chambers,  as 
previously  described,  could  be  found  readily  and  in  numbers.  If  the 
conditions  as  noted  this  season  are  normal,  then  the  worms  live  in  their 
winter  quarters  during  all  of  the  fall  and  winter  months,  remaining 
quiescent  for  fully  half  of  the  year. 

The  life  history  as  worked  out  in  this  investigation  is  graphically 
shown  in  the  accompanying  calendar. 


RESULTS   FROM   SPRAYING  EXPERIMENTS. 

As  the  summer  advanced  the  work  of  the  worms  in  the  fruit  became 
more  and  more  apparent,  until,  as  the  various  kinds  were  picked,  we 
were  able  to  determine  the  final  results  obtained  through  the  use  of 
various  spray  materials.  The  following  table  is  compiled  from  the 
detailed  record  of  the  experiments  on  the  five  station  orchards,  and 
from  work  done  on  twelve  other  selected  places  on  which  we  took  com- 
plete records.  Only  two  not-sprayed  places  are  directly  referred  to,  but 
the  heavy  loss  found  on  these  places  is  practically  the  same  as  found  on 
other  places  where  there  was  the  same  neglect  of  spraying.  The  per- 
centages of  loss  were  obtained  in  nearly  all  cases  from  actual  weights  of 
wormy  fruit,  though  in  a  few  instances  the  figures  represent  an  actual 
count  of  the  peaches. 


peach-worm:  spraying  experiments. 


33 


ALEXANDER.     Time  of  first  blossoms,  March  15. 


Designation 

of  Orchard.  Spray  Material. 

Ophir  Lime,  salt  and  sulfur 

Ophir  Check  trees . . 

A  Lime,  salt  and  sulfur ._ 

A  Check  tree.. 

B  Lime,  salt  and  sulfur 

C  Lime,  salt  and  sulfur ...  .. 

7  Lime,  salt  and  sulfur. . .  ...    .. 

8  Lime,  salt  and  sulfur 

9  Lime,  salt  and  sulfur.. .. 

10  Lime,  salt  and  sulfur..   

1  Lime,  salt  and  sulfur.. 

2  I  X  L  compound 

2,  resprayed  28°  dist.  emul.,  1  to  8  parts  water.. 

2,  resprayed  33°  dist.  emul.,  1  to  8  parts  water.. 

2,  resprayed  150°  kero.  emul.,  1  to  8  parts  water. 

3  I  X  L  compound 

3  Check  trees 

4  I  X  L  compound .. 

5  I  X  L  compound 

6  I  X  L  compound 

11  No  spray 

12  No  spray 


No 


Trees. 

50 

4 

150 

1 

50 
275 

50* 
100* 
220* 
300* 
110* 
300* 
100* 
100* 
100* 
300* 
5 
350* 
450* 
500* 
400* 
350* 


Time  of 
Spraying. 

Aprill 

Not  sprayed. .. 

March  12 

Not  sprayed... 

March  10 

March  10 

March  8 

March  8 

March  6 

March  10 

Feb.  1  to  6 

March  8 

May  15 

May  15 

May  15 

Mar.  7,  Apr.  6.. 
Not  sprayed... 
Mar.  8,  Apr.  9.. 
Mar.  10,  Apr.  10 
Mar.  8,  Apr.  7._ 


Per  Cent 
of  Loss. 

1 
50 

1 
35 

1 

3 

1 

1 

2 

15 
20 

6 

6 

8 
40 
40 
50 
65 
60 
60 
55 


HALE.    Time  of  first  blossoms,  March  15. 


Newcastle 

Newcastle 

Ophir 

Ophir 

A 

B 

C 

7 

8 

9 

10 

1 

2 

2,  resprayed 

2,  resprayed 

2,  resprayed 

3 

3 

4 

5 

6 

11 

12 


Lime,  salt  and  sulfur ... 

Check  trees , 

Lime,  salt  and  sulfur 

Check  tree 

Lime,  salt  and  sulfur ._ 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur _. 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

I  X  L  compound 

28°  dist.  emul.,  1  to  8  parts  water... 
33°  dist.  emul.,  1  to  8  parts  water  ... 
150°  kero.  emul.,  1  to  8  parts  water. 

I  X  L  compound 

Check  trees  ._ _ .... 

I  X  L  compound . 

I  X  L  compound 

I  X  L  compound 

TJnsprayed 

TJnsprayed 


500 
5 
200 
1 
900 
300 
550 
125* 
150* 
600* 
550* 
220 
250* 
85* 
85* 
80* 
150* 

5 
5O0* 
900* 
600* 
650* 
800* 


March  17,  18.. 
Not  sprayed .. 

March  31 

Not  sprayed  . . 
March  13,  14.. 

March  10 

March  8,  10  ... 

March  8 

March  12 

March  4,  5 

March  12,  13.. 
Feb.  1  to  6.... 

March  8 

May  15 

May  15 

May  15 

Mar.  6,  Apr.  3. 
Not  sprayed  .. 
Mar.  7,  Apr.  5. 
Mar.  7,  Apr.  2. 
Mar.  3,  Apr.  4. 


0 

55 

0 

40 
1 
1 
20 
1 
2 

14 
15 
25 

20 
20 
25 
45 
40 
65 
70 
60 
65 
55 


*  Approximate. 


3— Bul.  144 


34 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION. 


EARLY  CRAWFORD.    Time  of  first  blossoms,  March  10. 


Designation 
of  Orchard. 

Newcastle 

Ophir 

A 

7 

8 

9 

10 

1 

5 

11 

12 

2 

2,  resprayed 

2,  resprayed 


Newcastle 
Ophir 
A 
8 
9 
10 
1 
5 
B 


Spray  Material.  No.  Trees. 

Lime,  salt  and  sulfur  1,000 


Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur... 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

I  X  L  compound 

No  spray 

No  spray _ 

I  X  L  compound  ._ 

28°  dist.  emul.,  1  to  8  parts  water. 
33°  dist.  emul.,  1  to  8  parts  water. 


200 
200 
110* 
300* 
125* 
350* 
300* 
400* 
450 
400* 
130* 
65* 
65* 


Time  of 
Spraying. 

March  5,  7  .. 

April  1 

March  8 

March  7 

March  6,  7  . . 
March  3  .  ... 

March  3 

Feb.  lto6  .. 
March  3 


March  8 
May  15  . 
May  15  . 


SUSQUEHANNA.    Time  of  first  blossoms,  March  5. 


Lime,  salt  and  sulfur.. 
Lime,  salt  and  sulfur.. 
Lime,  salt  and  sulfur. 
Lime,  salt  and  sulfur.. 
Lime,  salt  and  sulfur.. 
Lime,  salt  and  sulfur.. 
Lime,  salt  and  sulfur.. 

I  X  L  compound 

Check  trees 


400 
200 
150 
200* 
250* 
125* 
200* 
250* 
2 


March  12  ... 

April  1 

March  3 

March  3 

March  1,  3  .. 
March  1,3... 
Feb.  lto  6  .. 
Mar.  4,  Apr.  I 
Not  sprayed. 


ST.  JOHN.       Time  of  first  blossoms,  February  24. 
IMPERIAL.    Time  of  first  blossoms,  February  25. 


Per  Cent 
of  Loss. 

0 

2 

1 

1 

2 

12 
15 
18 
45 
45 
40 

25 
25 


1 

1 

3 

1 

5 

15 

25 

30 

50 


Lime,  salt  and  sulfur. 
Lime,  salt  and  sulfur. 


900 
500 


Feb.  21. 
Feb.  20. 


FOSTER.    Time  of  first  blossoms,  March  5. 


Newcastle 
A 


Lime,  salt  and  sulfur.. 
Lime,  salt  and  sulfur.. 

8  Lime,  salt  and  sulfur.. 

9  Lime,  salt  and  sulfur.. 
10  Lime,  salt  and  sulfur.. 

resprayed   I  X  L  compound 

resprayed   28°  distillate  emulsion 
resprayed    28°  distillate  emulsion 


450 

350 

400* 

350* 

400* 

200 

100 

100 


March  1 
March  3 
March  3 
Feb.  28.. 
March  2 
March  8 
May  16. . 
May  16. . 


McDEVITT.    Time  of  first  blossoms,  March  2. 


Newcastle       Lime,  salt  and  sulfur. 


Ophir 
A 

C 

7 

8 

9    ' 
10 

1 
11 


Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur.. 

Lime,  salt  and  sulfur.. 

Lime,  salt  and  sulfur 300* 

Lime,  salt  and  sulfur 300* 

Lime,  salt  and  sulfur 150* 

Not  sprayed 400* 


330 

250 

400 

250* 

150* 

250* 


March  4  . . 
April  2.... 
Feb.  24  ... 
Feb.  27.... 

Feb.  24 

Feb.  24.... 
Feb.  23.... 

Feb.  25 

Feb.  1  to  6 


1 
3 
2 
6 
9 

20 
20 


1 
2 

18 
4 
5 
8 
7 
25 
50 


Approximate. 


peach-worm:  spraying  experiments. 


35 


LEVI.    Time  of  first  blossoms,  March  13. 


Designation 

of  Orchard.  Spray  Material. 

Newcastle  Lime,  salt  and  sulfur _. 

Ophir  Lime,  salt  and  sulfur 

Ophir  Check  trees 

A  Lime,  salt  and  sulfur 

B  Lime,  salt  and  sulfur 

C  Lime,  salt  and  sulfur 

8  Lime,  salt  and  sulfur 

9  Lime,  salt  and  sulfur .. 

10  Lime,  salt  and  sulfur 

1  Lime,  salt  and  sulfur 

2  I  X  L  compound 

2,  resprayed  28°  dist.  emul.,  1  to  8  parts  water. . 

2,  resprayed  33°  dist.  emul.,  1  to  8  parts  water.. 

2,  resprayed  150°  kero.  emul.,  1  to  8  parts  water 

3  I  X  L  compound 

4  I  X  L  compound 

5  I  X  L  compound  ... _ 

6  I  X  L  compound 

11  No  spray 

12  Lime,  salt  and  sulfur 


No.  Trees. 
650 
800 
3 
200 
500 
600 
300* 
350* 
400 
330 
350* 
125* 
115* 
110* 
250* 
200* 
350 
450 
600* 
450 


Time  of 
Spraying. 


March  13,  14  — 

April  2,  3. 

Not  sprayed... 

March  8 

March  8,  10 

March  6,  7 

March  9 

March  8 

March  12 

Feb.  lto6 

March  7 

Mayl5 

May  15 

May  15 

Mar.  8,  Apr.  2.. 
Mar.  6,  Apr.  4.. 
Mar.  6,  Apr.  5__ 
Mar.  7,  Apr.  6.. 

Mar.  10,  11 


Per  Cent 
of  Loss. 

0 

2t 
25 

2t 

It 

4t 

3 

4 
12 
25 

10 
10 
12 
40 
20 
35 
40 
45 
4 


SALWAY.    Time  of  first  blossoms,  March  15. 


Newcastle 

Newcastle 

Ophir 

Ophir 

A 

B 

C 

7 

8 

9 

10 

1 

Ophir 

Ophir 

2 

2,  resprayed 

2,  resprayed 

2,  resprayed 

3 

4 

5 

6 

11 

12 


Lime,  salt  and  sulfur 

Check  trees 

Lime,  salt  and  sulfur 

Check  trees 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur... 

Lime,  salt  and  sulfur _. . 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Lime,  salt  and  sulfur 

Distillate  emulsion^ 

Distillate  emulsion§ 

I  X  L  compound 

28°  dist.  emul.,  1  to  8  parts  water... 
33°  dist.  emul.,  1  to  8  parts  water... 
150°  kero.  emul.,  1  to  8  parts  water. 

I  X  L  compound ._ 

I  X  L  compound  

I  X  L  compound _ 

I  X  L  compound 

No  spray 

Lime,  salt  and  sulfur 


500 
4 
500 
3 
400 
500 
700 
300* 
550* 
450* 
450 
350 
48 
168 
560* 
190* 
185* 
185* 
150* 
350* 
500* 
450* 
300* 
500 


10.... 


March  12 

Not  sprayed. 

April  4.. 

Not  sprayed. 

March  7 

March  7 

March  5 

March  8 

March  8 

March  4 

March  7  . .. 
Feb.  1  to  6  . 
Feb.  12  .... 
March  31  .. 
March  7,  8 . 
May  15,  16 . 
May  15,  16 . 
May  15,  16  . 
Mar.  6,  Apr 
Mar.  6,  Apr 
Mar.  7,  Apr 


Mar.  7,  Apr.  9. 


1 

50 

0 

25 

2 

1 

5 

1 

2 

2 

5 

25 

50 

45 

18 
18 
18 
30 
25 
25 
40 
45 
4 


*  Approximate.       t  Estimate. 

I  Hercules  distillate  emulsion  1  to  8,  1  to  10,  and  1  to  12  parts  of  water,  sixteen  trees  each. 

$  Densmore-Stabler  untreated  28°  emulsion,  treated  28°  emulsion,  and  33°  emulsion,  1  to  10  and 
1  to  14  parts  of  water,  also  treated  distillate  oil  28°,  untreated  28°  oil,  and  33°  distillate,  1  to  3  and  1 
to  4  parts  of  water— fourteen  trees  each. 


36  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


UNSPRAYED    TREES. 

The  results  obtained  in  the  control  of  the  peach-worm  are  well  shown 
in  these  tables.  It  will  be  most  evident  that  the  season  of  1902  was 
one  in  which  the  worms  were  very  plentiful.  The  check-trees  in  every 
case  were  heavily  infested,  while  the  average  loss  among  unsprayed 
trees  indicates  the  presence  of  the  worms  in  disastrously  large  numbers. 

Bringing  together  the  unsprayed  trees  into  one  table,  we  see  this  fact 

very  evident. 

Percentage  of  Loss  on  Unsprayed  Trees. 

.  No.  of  Maximum  Minimum  Average 

variety.  Trees.  per  cent.  per  cent.  per  cent. 

Alexander 760  60  35  48 

Hale 1,461  65  40  49 

Early  Crawford 850  45  40  42 

Susquehanna. 2  50  50  50 

McDevitt... 400  50  45  47 

Levi .- 603  50  25  45 

Salway.. 307  50  25  45 

Total ._„ 4,884  65  25  48 


SPRAYED    TREES. 

The  Failure  of  the  I  X  L  Compound. — The  same  fact  is  further 
emphasized  in  the  case  of  the  use  of  the  I  X  L  compound,  which  proved 
to  be  an  utter  failure  as  a  means  of  controlling  the  peach-worm. 

Percentage  of  Loss  on  Trees  Sprayed  with  I  X  L  Compound. 

Varietv  ^°-  °*  Maximum  Minimum  Average 

Trees.  per  cent.  per  cent.  per  cent. 

Alexander 1,600  65  40  53 

Hale 2,150  70  45  60 

Early  Crawford 400  45  45  45 

Susquehanna _.  250  30  30  30 

Levi • 1,250  40  20  35 

Salway 1,450  40  25  37 

Total.... 7,100  70  20  50 

These  results  are  very  conclusive,  both  because  of  the  large  number  of 
trees  concerned,  and  because  the  timing  of  the  application  was  the  same 
as  that  which  gave  the  best  results  with  the  lime,  salt  and  sulfur. 

The  Use  of  Oil  for  Killing  the  Pupae. — The  results  obtained  from  the 
use  of  the  distillate  emulsions  and  kerosene-oil  emulsions,  following  the 
spring  use  of  the  I  X  L  compound,  indicate  a  considerable  saving  over 
the  loss  that  would  have  resulted  from  depending  upon  that  compound. 
That  this  result  would  have  been  quite  as  good  had  the  I  X  L  compound 
spraying  been  omitted,  seems  more  than  probable,  when  we  remember 
that  the  bud-worm  attack  was  so  severe  on  the  place  that  it  appeared  at 
the  time  that  this  material  had  in  nowise  controlled  the  pests  in  this 
stage.     The  results  of  this  work  with  the  distillate  and  kerosene  emul- 


peach-worm:  effects  of  sprays. 


37 


sions  were  certainly  good  enough  to  warrant  their  use,  and  will  be  useful 
to  fruit-growers  in  the  future,  if  by  any  chance  they  fail  to  spray  at  the 
proper  time,  and  find  that  the  worms  are  pupating  in  too  great  numbers 
on  the  trunks  and  larger  limbs  of  the  trees,  as  is  their  habit  in  the 
spring  generation. 

Loss  When  Sprayed  in  March  with  I  X  L  Compound,  and  in  May  with  Emulsions 
of  Distillate  and  of  Kerosene. 

Varietv  No-  of         Maximum     Minimum        Average 

y"  Trees.  per  cent.        per  cent.       per  cent. 

Alexander _ .  _ 300  8  6  7 

Hale.... 250  25  20  21 

Foster ...  200  20  20  20 

Levi 350  12  10  11 

Salway 560  18  18  18 

Total 1,460  25  6  15 

Winter  Spraying  with  Lime,  Salt  and  Sulfur. — When  compared  with 
the  loss  where  no  spraying  has  been  the  practice,  the  winter  use  of  the 
lime,  salt  and  sulfur,  as  shown  on  orchard  No.  1,  results  in  a  certain 
amount  of  control  of  the  worm.  The  results  are  by  no  means  satis- 
factory, for  while  a  great  deal  better  than  either  of  the  treatments  given 
above,  still  the  work  does  not  result  in  the  reduction  of  the  loss  to  a  low 
enough  minimum. 

Loss  When  Sprayed  in  Winter  with  Lime,  Salt  and  Sulfur. 

Variptv  No-  of         Maximum     Minimum        Average 

vaneiy.  Trees.  per  cent.        per  cent.        per  cent. 

Alexander 110  20  20  20 

Hale 220  25  25  25 

Early  Crawford 300  18  18  18 

Susquehanna 200  25  25  25 

McDevitt T 150  25  25  25 

Levi.... 330  25  25  25 

Salway 350  25  25  25 

Total 1,660  25  18  24 

Spring  Spraying  with  Lime,  Salt  and  Sulfur. — The  best  results  were 
obtained  by  the  use  of  lime,  salt  and  sulfur  compound,  as  shown  by  the 
following  table: 

Loss  when  Sprayed  in  Spring  with  Lime,  Salt  and  Sulfur. 

Variptv  ^°-  °*  Maximum  Minimum        Average 

y"  Trees.  per  cent.  per  cent.       per  ceut. 

Alexander 1,195  15  0                    4 

Hale  4,175  15  0                     5 

Early  Crawford 2,285  15  0                    5 

St.  John  and  Imperial 1,400  2  0                    1 

Susquehanna..-. 1,325  15  1                    3 

Foster 1,950  9  14 

McDevitt 2,230  18  1                     6 

Levi 3,800  12  0                     3 

Salway 4,300  5  12 

Total 22,660  18  0  3 


38  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

In  some  respects  the  above  table  fails  to  give  a  correct  idea  of  the 
results  from  the  use  of  this  mixture  at  the  right  time,  since  it  includes 
two  orchards,  station  C  and  orchard  No.  10,  in  which  the  conditions 
were  very  unfavorable  for  producing  good  results.  With  these  two 
orchards  eliminated,  the  average  amount  of  injury  shown  by  the  tables 
would  not  be  over,  one  per  cent.  Even  when  they  are  included  the 
efficiency  of  this  treatment  as  compared  with  the  others  is  very 
strikingly  shown  in  the  fullowing  table: 

Comparative  Statement  of  Loss  by  Different  Treatments. 

Spraying  Material.  £°-  of  Maximum  Minimum  Average 

J  Trees.  per  cent.  per  cent.  per  cent. 

Not  sprayed 4,884  65                  25  48 

I  X  L  compound 7,100  70                  20  50 

I  X  L  compound  and  distillate . .  1,460  25                    6  15 

Winter  lime,  salt  and  sulfur 1,660  25                  18  24 

Spring  lime,  salt  and  sulphur 22,660  18                     0  3 

MISCELLANEOUS    RESULTS. 


l/n  sprayed 
peach 

orchard 
No  13 

Loss 

40  to  50  f 


-r-^To  Loomis       "S 


Un sprayed 
peach 
orchard 

NO.  1 1 

Loss 
60  to  65/. 


younj)  peach. 

orchard 
urn  prayed 
AU  fruit 

wormy     //*§ 

no.ia 


Sprayed 
peach 
orchard 
Loss 


Loss  Due  to  Adjacent  Infested  Orchards. — The  results  obtained  at 
station  C  show  plainly  the  danger  from  careless  neighbors.  The  location 
of  this  station  is  in  a  district  where  spraying  is  not  the  rule,  and  where 

the  loss  from  wormy  fruit  is 
/  usually  very  heavy.    When 

the  place  was  selected  for 
these  experiments  it  was 
found  to  be  well  stocked 
with  hibernating  larvae. 
The  orchard  had  been 
sprayed  the  previous  year 
with  the  lime,  salt  and  sul- 
fur compound.  The  loss  of 
fruit  last  year  was  reported 
to  us  as  being  "  very  heavy." 
Spraying  operations  were 
begun  in  this  orchard  when 
the  buds  had  swollen  and 
were  nearly  ready  to  burst 
out.  The  lime,  salt  and 
sulfur  compound  was  pre- 
pared by  the  owner  with  great  care  and  the  trees  thoroughly  treated- 
While  the  material  used  and  the  method  and  time  of  application  were 
in  accordance  with  the  best  practice,  yet  when  the  crop  was  picked  it 
was  found  that  there  was  a  heavy  loss  from  wormy  fruit. 

The  location  of  this  orchard  and  the  relative  losses  here  and  in  neigh- 
boring orchards  are  shown  in  Fig.  15.     The  loss  in  the  sprayed  place  is 


Fig.  15.    Loss  caused  by  adjacent  unsprayed  orchard. 


peach-worm:    spraying  methods. 


39 


very  much  less,  as  will  be  noted,  than  in  the  unsprayed  orchards, 
though  it  is  much  greater  than  in  the  orchards  more  favorably  located 
as  to  neighbors. 


Loss  from  Careless  Work. — Orchard  No.  10  was  selected  and  the  records 
kept  because  it  was  a  good  illustration  of  the  results  of  carelessly  spray- 
ing the  trees.  This  orchard  was  worked  by  Chinese  renters  under  a 
lease  requiring  them  to  spray  the  place  each  year.     The  work  was  done, 


40  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

however,  in  the  most  perfunctory  manner.  We  visited  the  place  a 
number  of  times  while  spraying  was  under  way,  and  gave  the  matter 
careful  attention.  The  lime,  salt  and  sulfur  mixture  was  used,  but 
was  made  up  in  a  way  that  rendered  it  practically  useless.  All  of  the 
materials,  except  the  water,  were  being  used  in  reduced  quantities,  and 
the  mixture  was  scarcely,  or  not  all,  boiled.  The  loss  found  here  can  be 
directly  traced  to  this  carelessness.  This  orchard  No.  10  lies  next  to  the 
station  A,  on  which  the  loss  was  very  small. 

The  tables  will  show  the  loss  sustained  in  orchard  No.  10  to  be  con- 
siderable, but  it  would  not  have  been  strange,  when  the  method  of 
spraying  is  taken  into  account,  if  it  had  been  still  greater. 

Saving  by  Careful  Work. — As  a  contrast  to  these  last  two  places,  we 
may  cite  the  orchard  we  have  called  station  A.  The  owners  of  this 
orchard  had  suffered  a  heavy  loss  the  previous  year  from  wormy  fruit. 
The  trees  were  found  much  infested  with  the  hibernating  larvae  when 
inspected  in  January.  We  were  able  to  have  the  work  of  spraying  done 
in  the  most  careful  manner  on  this  place.  Fig.  16  shows  one  of  the 
spraying  outfits  used  at  this  place. 

The  contrast  between  this  orchard  and  orchard  No.  10  was  very 
striking.  As  previously  noted,  these  two  orchards  lie  adjacent  to  each 
other.  On  three  rows  of  Hales  next  to  the  poorly-sprayed  place  the  loss 
was  from  five  to  ten  times  greater  than  the  loss  in  the  orchard  as  a 
whole.  Without  doubt  this  was  due  to  the  flight  of  the  moths  from 
orchard  No.  10.     Similar  instances  were  noted  in  several  cases. 

The  Use  of  Oil  and  Distillate  Emulsion. — A  small  number  of  experi- 
ments not  noted  in  the  above  tables  indicate  that  the  emulsions  of 
kerosene  and  the  distillate  oils,  when  used  in  the  early  spring,  produced 
a  good  degree  of  control,  though  hardly  as  good  as  when  the  lime,  salt 
and  sulfur  were  used  under  identical  conditions.  Experiments  with 
these  materials  are  to  be  conducted,  however,  on  a  commercial  scale,  in 
order  to  demonstrate  their  real  value  for  spring-spraying  purposes. 

The  value  of  these  substances,  as  used  against  the  pupa?  of  the  first 
generation,  is  clearly  shown.  It  should  not  be  made  the  sole  depend- 
ence, but  rather  to  enable  the  grower  to  have  another  chance  at  killing 
the  insect,  when  for  any  cause  the  first,  or  spring,  spraying  has  been 
omitted  or  found  ineffective.  This  treatment  should  be  so  timed  in  the 
late  spring  that  pupation  will  be  well  under  way,  as  determined  by 
careful  inspection  of  the  trees  at  that  time. 

The  distillate  oils  are  prepared  in  emulsions  by  certain  manufacturers, 
and  are  quite  cheap  and  effective.  The  oils  themselves  are  quite  readily 
emulsified.     We  have  found  the  following  formula  useful: 

Distillate  oil  (28°  or  33°-35°) 5  gallons. 

Common  kitchen  soap 4  to  6  pounds. 


peach-worm:    spraying  methods. 


41 


Dissolve  the  soap  in  about  four  gallons  of  hot  water.  Pour  the  oil 
into  the  hot  suds,  and  thoroughly  churn  the  two  together  by  pumping 
the  material  back  into  itself  through  a  spray  pump.  In  from  ten  to 
fifteen  minutes  the  material  will  be  thoroughly  emulsified,  and  will  be 
of  a  creamy  color  and  consistency.     In  this  condition  it  readily  mixes 


Fig.  17.    Boiling  the  lime,  salt  and  sulfur  spray. 


>??.  '- 

,TV: 

H| 

'      HAk         ^l^dft                BK&M 

w^ww^ 

.          /,^      -      - 

Fig.  18.    Wheeled  sled  and  tank  spraying  outfit. 

with  water.     To  use,  dilute  in  the  proportion  of  one  of   emulsion  to 
eight  of  water,  using  hot  water  preferably.     Apply  to  the  trees  warm. 

The  kerosene-oil  emulsion  may  be  prepared  in  the  same  way,  but 
using  no  more  than  four  pounds  of  soap.  It  is  to  be  used  in  the 
same  way  as  the  distillate  emulsion,  but  is  not  quite  as  effective  as  the 
latter. 

4— Bul.  144 


42  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

GENERAL  CONCLUSIONS  AND  RECOMMENDATIONS. 

The  experiments  reported  in  this  bulletin  prove  that  the  peach-worm 
can  be  controlled  by  the  use  of  the  lime,  salt  and  sulfur  compound,  if 
this  material  is  prepared  in  the  proper  manner  and  thoroughly  applied 
at  the  right  time.  These  three  factors  are  all  essential  to  successful 
treatment. 

The  formula  for  the  preparation  of  the  lime,  salt  and  sulfur  spray,  as 
used  successfully  in  the  Placer  County  region  this  season,  is  as  follows: 

Lime — — 40  pounds. 

Sulfur 20  pounds. 

Salt . - 15  pounds. 

Water,  to  make 60  gallons. 

Boil  10  pounds  of  lime  and  20  pounds  of  sulfur  in  20  gallons  of  water 
for  from  one  and  one  half  to  two  hours,  or  until  the  mixture  is  a  deep 
amber  color,  which  will  indicate  that  the  sulfur  is  dissolved.  The 
balance  of  the  lime,  30  pounds,  should  then  be  slaked  in  another  vessel 
and  the  salt  added  to  this  latter  mixture.  This  should  be  stirred  until 
the  salt  is  dissolved  and  then  added  to  the  original  mixture  of  lime  and 
sulfur,  and  the  whole  boiled  for  from  thirty  to  forty-five  minutes  longer, 
enough  water  being  added  to  bring  the  total  amount  of  material  up  to 
60  gallons.  Next  strain  the  material  into  the  spray  tank  and  apply  to 
the  trees  hot.  Do  not  let  the  material  get  cold,  for  a  portion  of  the 
ingredients  will  then  crystallize  and  precipitate  out  of  the  liquid,  and 
its  effectiveness  is  much  reduced.  Many  different  arrangements  for 
boiling  the  spray  are  used,  and  each  orchardist  will  devise  the  method 
most  convenient  to  him.  We  found  the  device  shown  in  Fig.  17  a  con- 
venient arrangement.  In  this  case  a  large  iron  cauldron  was  set  up  on 
an  iron  frame,  so  made  that  the  bottom  of  the  cauldron  was  about  one 
foot  above  the  ground,  when  the  device  was  ready  for  use.  A  fire  could 
then  be  easily  built  beneath  the  cauldron  and  the  boiling  thoroughly 
done.  When  it  is  not  necessary  to  move  the  cauldron,  it  is  well  to  build 
up  a  stone  or  brick  fireplace  beneath  it,  so  arranged  that  a  good  draft 
can  be  maintained. 

As  to  the  apparatus  for  spraying,  one  may  employ  any  of  the  outfits  of 
pumps,  etc.,  commonly  sold  for  use  in  orchards.  Two  such  outfits  are 
shown  in  Figs.  16  and  18,  from  photographs  taken  in  the  orchards  this 
spring. 

The  important  thing  in  spraying  work  is  to  completely  cover  every 
tree  with  the  material  used.  This  thorough  work  must  be  insisted  on 
as  a  requisite  for  successful  control  of  the  worm.  The  hibernating 
burrows  in  which  the  worms  are  hiding  at  this  season  may  be  found  in 
any  part  of  the  tree — from  the  tips  of  the  topmost  branches  to  the 
ground. 


peach-worm:  general  conclusions. 


43 


o 


44  UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 

The  time  to  make  the  application  varies  with  the  variety.  It  should 
be  done  when  the  buds  have  begun  to  swell  perceptibly,  and  it  may  be 
delayed,  without  serious  injury  to  the  tree,  until  after  the  blossoms  have 
begun  to  appear,  at  least  .under  the  conditions  found  in  Placer  County 
during  the  past  season. 

The  effectiveness  of  such  treatment  can  now  be  considered  to  be  an 
established  fact. 


